ISESteroids Theme Template that has comments for easy theme creation. I used plain xml extension to get syntax highlighting working. To use you will need to rename to ThemeName.ISESteroidsThemeXML. For more detailed information you can visit my blog: http://brandonpadgett.com/powershell/isesteroids-theming/

ISESteroidsThemeTemplate.xml

<?xml version="1.0"?>
<ColorOptions xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <!-- For more detailed information you can visit my blog  -->
  <!-- http://brandonpadgett.com/powershell/isesteroids-theming/ -->
  
  <!-- Shares Console and Script Pane Settings -->
  <ShareFontForConsole>false</ShareFontForConsole>
  
  <!-- Script Pane Font Settings -->
  <ScriptPaneFontFamily>ubuntumono-r.ttf#Ubuntu Mono</ScriptPaneFontFamily>
  <ScriptPaneFontSize>12</ScriptPaneFontSize>
  
  <!-- Console Pane Font Setings -->
  <ConsolePaneFontFamily>sourcecodepro-regular.ttf#Source Code Pro</ConsolePaneFontFamily>
  <ConsolePaneFontSize>10</ConsolePaneFontSize>
  
  <!-- Console Pane Background and Text Colors -->
  <ConsolePaneForegroundColor>#FFEEEEEC</ConsolePaneForegroundColor>
  <ConsolePaneBackgroundColor>#FF212121</ConsolePaneBackgroundColor>
  
  <!-- Sets the Console Text and Text Background Colors for Error Messages -->
  <ConsolePaneErrorForegroundColor>#FFEF2929</ConsolePaneErrorForegroundColor>
  <ConsolePaneErrorBackgroundColor>#00FFFFFF</ConsolePaneErrorBackgroundColor>
  <!-- Sets the Console Text and Text Background Colors for Warning Messages -->
  <ConsolePaneWarningForegroundColor>#FFC4A000</ConsolePaneWarningForegroundColor>
  <ConsolePaneWarningBackgroundColor>#00FFFFFF</ConsolePaneWarningBackgroundColor>
  <!-- Sets the Console Text and Text Background Colors for Verbose Messages -->
  <ConsolePaneVerboseForegroundColor>#FF06989A</ConsolePaneVerboseForegroundColor>
  <ConsolePaneVerboseBackgroundColor>#00FFFFFF</ConsolePaneVerboseBackgroundColor>
  
  <!-- Script Pane Background Color -->
  <ScriptPaneBackgroundColor>#FF212121</ScriptPaneBackgroundColor>
  
  <!-- This Sets All Caps for Menu Header -->
  <CapitalizeMainMenuHeaders>false</CapitalizeMainMenuHeaders>
  
  <!-- This is the selection color -->
  <ActiveSelection>#B1F92672</ActiveSelection>
  <!-- This is color when above selection is not focused -->
  <InactiveSelection>#FFBFCDDB</InactiveSelection>
  
  <!-- For Solid Color or Gradient Color Background -->
  <MenuBarMonochrome>true</MenuBarMonochrome>
  <!-- For Solid Color Background with Monochrome = True -->
  <MenuBarColor1>#FFA8A8A8</MenuBarColor1>
  <!-- For Gradient Background Colors if Monochrome = False -->
  <MenuBarColor2>#FFE6F0FA</MenuBarColor2>
  <MenuBarColor3>#FFF8FAFC</MenuBarColor3>
  <MenuBarColor4>#FFDCE6F4</MenuBarColor4>
  <MenuBarColor5>#FFE1ECF9</MenuBarColor5>
  <MenuBarColor6>#FFF8FAFC</MenuBarColor6>
  
  <!-- For Square Tabs -->
  <ScriptSquareTabs>true</ScriptSquareTabs>
  
  <!-- For Solid Color or Gradient Color Background -->
  <ScriptSelectedMonochrome>true</ScriptSelectedMonochrome>
  <!-- For Solid Color Background if Monochrome = True -->
  <ScriptSelectedColor1>#FFA8A8A8</ScriptSelectedColor1>
  <!-- For Gradient Background Colors if Monochrome = False -->
  <ScriptSelectedColor2>#FFFFFFFF</ScriptSelectedColor2>
  <ScriptSelectedColor3>#FFDFE9FC</ScriptSelectedColor3>
  <ScriptSelectedColor4>#FFE1EEFC</ScriptSelectedColor4>
  
  <!-- For Solid Background Color or Gradient Color Background -->
  <ScriptUnselectedMonochrome>true</ScriptUnselectedMonochrome>
  <!-- For Solid Color Background if Monochrome = True -->
  <ScriptUnselectedColor1>#FFB6B6B6</ScriptUnselectedColor1>
  <!-- For Gradient Colors if Monochrome = False -->
  <ScriptUnselectedColor2>#FFEBEBEB</ScriptUnselectedColor2>
  <ScriptUnselectedColor3>#FFDDDDDD</ScriptUnselectedColor3>
  <ScriptUnselectedColor4>#FFCDCDCD</ScriptUnselectedColor4>
  
  <!-- Used for the Arrow in the Group Overflow -->
  <ToolbarOverflowButtonBackground>#FFA5A5A5</ToolbarOverflowButtonBackground>
  <!-- This is the Button Group Background Color for the Run/Debug Area -->
  <ToolbarOverflowButtonBackgroundForRunCode>#FFA8A8A8</ToolbarOverflowButtonBackgroundForRunCode>
  <ToolbarOverflowButtonBackgroundForDebugger>#FFA8A8A8</ToolbarOverflowButtonBackgroundForDebugger>
  <!-- Color of the Button Groups Background -->
  <ToolbarGroupBackground>#FFA8A8A8</ToolbarGroupBackground>
  <!-- This is the Group Background Color for the Run/Debug Group  -->
  <ToolbarGroupBackgroundForRunCode>#FFA8A8A8</ToolbarGroupBackgroundForRunCode>
  <ToolbarGroupBackgroundForDebugger>#FFA8A8A8</ToolbarGroupBackgroundForDebugger>
  
  <!-- This is the Border Color -->
  <RunspaceBarBackground>#FFA8A8A8</RunspaceBarBackground>
  
  <!-- For Solid Color or Gradient Color Background -->
  <ScriptExpanderMonochrome>true</ScriptExpanderMonochrome>
  <!-- For Solid Color Background if Monochrome = True -->
  <ScriptExpanderColor1>#FFD4D4D4</ScriptExpanderColor1>
  <!-- For Gradient Colors if Monochrome = False -->
  <ScriptExpanderColor2>#FFD4D4D4</ScriptExpanderColor2>
  <ScriptExpanderColor3>#FFC5C5C5</ScriptExpanderColor3>
  <ScriptExpanderColor4>#FFC5C5C5</ScriptExpanderColor4>
  <ScriptExpanderColor5>#FFB6B6B6</ScriptExpanderColor5>
  <ScriptExpanderColor6>#FFB6B6B6</ScriptExpanderColor6>
  
  <!-- For Solid Color or Gradient Color Background -->
  <EditorTabControlMonochrome>true</EditorTabControlMonochrome>
  <!-- For Solid Color Background if Monochrome = True -->
  <EditorTabControlColor1>#FF3B3B3B</EditorTabControlColor1>
  <!-- For Gradient Colors if Monochrome = False -->
  <EditorTabControlColor2>#FFE6F0FA</EditorTabControlColor2>
  
  <!-- Border Trim Color -->
  <EditorTabControlBackground>#FF3B3B3B</EditorTabControlBackground>
 
  <!-- Script Saved State Gutter Colors -->
  <DebuggerMarginUnsavedScript>#FFF92672</DebuggerMarginUnsavedScript>
  <DebuggerMarginSavedScript>#FF333333</DebuggerMarginSavedScript>
  
  <!-- Script Debugger State Colors -->
  <DebuggerMarginDebuggerActive>#FFBAC023</DebuggerMarginDebuggerActive>
  <DebuggerMarginDebuggerActiveBackground>#FF000000</DebuggerMarginDebuggerActiveBackground>
  
  <!-- Current Line Arrow Colors -->
  <CurrentLineAdornmentBorder>#0047E7C1</CurrentLineAdornmentBorder>
  <CurrentLineAdornmentFill>#FF565657</CurrentLineAdornmentFill>
  
  <!-- Squiggle Colors -->
  <SquiggleSyntaxError>#FFFF0000</SquiggleSyntaxError>
  <SquiggleMinorWarning>#FF008000</SquiggleMinorWarning>
  <SquiggleCriticalWarning>#FF0000FF</SquiggleCriticalWarning>
  <SquiggleIncompatibility>#FFFEFF00</SquiggleIncompatibility>
  
  <!-- Gutter Change Colors -->
  <TrackChangesBeforeSave>#FFDAA520</TrackChangesBeforeSave>
  <TrackChangesAfterSave>#FF2E8B57</TrackChangesAfterSave>
  <TrackRevertedChanges>#FF0000FF</TrackRevertedChanges>
  
  <!-- Line Number Margin Size -->
  <LineNumberMarginSize>13</LineNumberMarginSize>
  <!-- Line Number Color -->
  <LineNumberMarginForegroundColor>#4CF0F0F0</LineNumberMarginForegroundColor>
  <!-- Selected Line Number Color -->
  <LineNumberMarginSelectedForegroundColor>#FFFD971F</LineNumberMarginSelectedForegroundColor>
  <!-- Bookmark Color -->
  <LineNumberMarginBookmarkColor>#B400DC00</LineNumberMarginBookmarkColor>
  <!-- Line Number Function Color -->
  <LineNumberMarginFunctionForegroundColor>#FFA6E22E</LineNumberMarginFunctionForegroundColor>
  <!-- Current Line Number Color -->
  <LineNumberMarginCurrentForegroundColor>#FFF92672</LineNumberMarginCurrentForegroundColor>
  <!-- Line Number Font Type -->
  <LineNumberMarginFontFamily>Segoe UI</LineNumberMarginFontFamily>
  
  <!-- Function Reference Font Settings-->
  <FunctionReferenceSize>10</FunctionReferenceSize>
  <FunctionReferenceFontFamily>DIN</FunctionReferenceFontFamily>
  
  <!-- Snippet Font Settings -->
  <SnippetFontFamily>Segoe UI</SnippetFontFamily>
  <SnippetFontSize>8</SnippetFontSize>
  
  <!-- Function Reference Color Settings -->
  <FunctionReferenceInactive>#FFD3D3D3</FunctionReferenceInactive>
  <FunctionReferenceActive>#FFAE81FF</FunctionReferenceActive>
  <FunctionReferenceHoverBackground>#6433EBBF</FunctionReferenceHoverBackground>
  
  <!-- Snippet Color settings when a Snippet has been added -->
  <SnippetHeader>#FFF92672</SnippetHeader>
  <SnippetDescription>#FFAE81FF</SnippetDescription>
  <SnippetBorder>#FFFD971F</SnippetBorder>
  
  <!-- Sets the Default Color of the Status Bar -->
  <StatusBarBackgroundInactive>#FF3B3B3B</StatusBarBackgroundInactive>
  <!-- The Color of the Status Bar when Powershell is Actively Running -->
  <StatusBarBackgroundActive>#FF3B3B3B</StatusBarBackgroundActive>
  
  <!-- Sets the Color of the Status Bar Text when Powershell is Actively Running -->
  <StatusBarForegroundColorActive>#FFFFFFFF</StatusBarForegroundColorActive>
  <!-- Set the Default Color of the Status Text -->
  <StatusBarForegroundColorInactive>#FFFFFFFF</StatusBarForegroundColorInactive>
  
  <!-- Sets the Default hyperlink Color -->
  <StatusBarHyperlinkDefaultColor>#FFA6E22E</StatusBarHyperlinkDefaultColor>
  <!-- Sets the Hover hyperlink Color -->
  <StatusBarHyperlinkHoverColor>#FFF92672</StatusBarHyperlinkHoverColor>
  <!-- Sets the Underline Preference -->
  <StatusBarHyperlinkUnderlineAlways>false</StatusBarHyperlinkUnderlineAlways>
  <!-- Sets the Hover Underline Preference -->
  <StatusBarHyperlinkUnderlineOnHover>false</StatusBarHyperlinkUnderlineOnHover>
  
  <!-- Collapsed Text Color -->
  <CollapsedTextColor>#FF59646F</CollapsedTextColor>
  <!-- Bar in Margin when Hovering -->
  <CollapseBarColor>#FFFF980F</CollapseBarColor>
  <!-- Background of highlighted expandable text -->
  <CollapseSelectionBackground>#17FFFFFF</CollapseSelectionBackground>
  <!-- Margin Square Color -->
  <CollapseSquareBackground>#FF66D9EF</CollapseSquareBackground>
  
  <!-- Function/Search Area Background Color -->
  <FunctionComboCollapsedFill>#FF3B3B3B</FunctionComboCollapsedFill>
  <!-- Function/Search Area Dropdown Background Color -->
  <FunctionComboExpandedFill>#FF3B3B3B</FunctionComboExpandedFill>
  <!-- Function/Search Area Dropdown Text Color -->
  <FunctionComboForeground>#AAFFFFFF</FunctionComboForeground>
  
  <!-- Function/Search Area Text Color -->
  <FunctionComboForegroundStatic>#FFD3D3D3</FunctionComboForegroundStatic>
  
  <!-- For Solid Color or Gradient Color Background -->
  <VerticalSplitterMonochrome>true</VerticalSplitterMonochrome>
 <!-- Border Color -->
  <VerticalSplitterBorder>#FF272827</VerticalSplitterBorder>
  <!-- For Solid Color Background if Monochrome = True -->
  <VerticalSplitterColor1>#FF272827</VerticalSplitterColor1>
  <!-- For Gradient Colors if Monochrome = False -->
  <VerticalSplitterColor2>#FFA2CBF3</VerticalSplitterColor2>
  <VerticalSplitterColor3>#FFB7CEF5</VerticalSplitterColor3>
  <VerticalSplitterColor4>#FFC6D2DE</VerticalSplitterColor4>
  
  <!-- For Solid Color or Gradient Color Background -->
  <HorizontalSplitterMonochrome>true</HorizontalSplitterMonochrome>
  <!-- Border Color -->
  <HorizontalSplitterBorder>#FF272827</HorizontalSplitterBorder>
  <!-- For Solid Color Background if Monochrome = True -->
  <HorizontalSplitterColor1>#FF272827</HorizontalSplitterColor1>
  <!-- For Gradient Colors if Monochrome = False -->
  <HorizontalSplitterColor2>#FFA2CBF3</HorizontalSplitterColor2>
  <HorizontalSplitterColor3>#FFB7CEF5</HorizontalSplitterColor3>
  <HorizontalSplitterColor4>#FFC6D2DE</HorizontalSplitterColor4>
  
  <!-- Text Color Settings -->
  <DefaultTextColor>#FFFFFFFF</DefaultTextColor>
  <DefaultTokenColor>#FFFFFFFF</DefaultTokenColor>
  
  <!-- Script Pane Syntax Settings -->
  <PowerShellScriptToken>
    <Token Name="Attribute" Color="#F92672" />
    <Token Name="Command" Color="#66D9EF" />
    <Token Name="CommandArgument" Color="#A6E22E" />
    <Token Name="CommandParameter" Color="#FFF5F5F5" />
    <Token Name="Comment" Color="#75715E" />
    <Token Name="GroupEnd" Color="#FFF5F5F5" />
    <Token Name="GroupStart" Color="#FFF5F5F5" />
    <Token Name="Keyword" Color="#F92672" />
    <Token Name="LineContinuation" Color="#FFF5F5F5" />
    <Token Name="LoopLabel" Color="#FFE0FFFF" />
    <Token Name="Member" Color="#FFF5F5F5" />
    <Token Name="NewLine" Color="#FFF5F5F5" />
    <Token Name="Number" Color="#AE81FF" />
    <Token Name="Operator" Color="#FFD3D3D3" />
    <Token Name="Position" Color="#FFF5F5F5" />
    <Token Name="StatementSeparator" Color="#FFF5F5F5" />
    <Token Name="String" Color="#E6DB74" />
    <Token Name="Type" Color="#A6E22E" />
    <Token Name="Unknown" Color="#FFF5F5F5" />
    <Token Name="Variable" Color="#FD971F" />
  </PowerShellScriptToken>
  
  <!-- Console Pane Syntax Settings -->
  <PowerShellConsoleToken>
    <Token Name="Attribute" Color="#F92672" />
    <Token Name="Command" Color="#66D9EF" />
    <Token Name="CommandArgument" Color="#A6E22E" />
    <Token Name="CommandParameter" Color="#FFF5F5F5" />
    <Token Name="Comment" Color="#75715E" />
    <Token Name="GroupEnd" Color="#FFF5F5F5" />
    <Token Name="GroupStart" Color="#FFF5F5F5" />
    <Token Name="Keyword" Color="#F92672" />
    <Token Name="LineContinuation" Color="#FFF5F5F5" />
    <Token Name="LoopLabel" Color="#FFE0FFFF" />
    <Token Name="Member" Color="#FFF5F5F5" />
    <Token Name="NewLine" Color="#FFF5F5F5" />
    <Token Name="Number" Color="#AE81FF" />
    <Token Name="Operator" Color="#FFD3D3D3" />
    <Token Name="Position" Color="#FFF5F5F5" />
    <Token Name="StatementSeparator" Color="#FFF5F5F5" />
    <Token Name="String" Color="#E6DB74" />
    <Token Name="Type" Color="#A6E22E" />
    <Token Name="Unknown" Color="#FFF5F5F5" />
    <Token Name="Variable" Color="#FD971F" />
  </PowerShellConsoleToken>
  
  <!-- XML Syntax Settings -->
  <XMLToken>
    <Token Name="Comment" Color="#FF6E715E" />
    <Token Name="CommentDelimiter" Color="#FFFFFFFF" />
    <Token Name="ElementName" Color="#FFFD971F" />
    <Token Name="MarkupExtension" Color="#FFFD971F" />
    <Token Name="Attribute" Color="#FFA6E22E" />
    <Token Name="Quote" Color="#FFFFFFFF" />
    <Token Name="QuotedString" Color="#FFE6DB74" />
    <Token Name="Tag" Color="#FFFFFFFF" />
    <Token Name="Text" Color="#FFFFFFFF" />
    <Token Name="CharacterData" Color="#FFFFFFFF" />
  </XMLToken>
  
  <!-- Bracket Colors -->
  <BraceMatchingFill>#B1F92672</BraceMatchingFill>
  <BraceMatchingBorder>#FFF92672</BraceMatchingBorder>
  
  <!-- Border Color of Selected Lines -->
  <ASTDashLineColor>#AAFFE4B5</ASTDashLineColor>
  
  <!-- Sibling Color Settings -->
  <ASTSiblingBorder>#00F7C93C</ASTSiblingBorder>
  <ASTSiblingFill>#4E6EA6CC</ASTSiblingFill>
  
  <!-- Scope Border Settings -->
  <ASTScopeBorder>#64FFE4B5</ASTScopeBorder>
  <ASTScopeFill>#22E5008E</ASTScopeFill>
  
  <!-- Pipeline Color Settings -->
  <ASTPipelineBorder>#50C8C814</ASTPipelineBorder>
  <ASTPipelineFill>#00F0F0E6</ASTPipelineFill>
  
  <!-- Color of Snippets when Typed -->
  <SnippetInsertionBorder>#FF038567</SnippetInsertionBorder>
  <SnippetInsertionFill>#FFAE81FF</SnippetInsertionFill>
  
  <!-- Console Admin Warning Settings -->
  <ConsoleAdminWarningColor1>#60FF9600</ConsoleAdminWarningColor1>
  <ConsoleAdminWarningColor2>#0047E7C1</ConsoleAdminWarningColor2>
  <ConsoleAdminWarningStripeOffset>5</ConsoleAdminWarningStripeOffset>
  
  <!-- Color Picker Palette Colors -->
  <PaletteColor1>#FF012456</PaletteColor1>
  <PaletteColor2>#FF283855</PaletteColor2>
  <PaletteColor3>#FFA9A9AB</PaletteColor3>
  <PaletteColor4>#FFC0D8EF</PaletteColor4>
  <PaletteColor5>#FFFFE1CE</PaletteColor5>
  <PaletteColor6>#FFE6F0FA</PaletteColor6>
  <PaletteColor7>#FFBAC023</PaletteColor7>
  <PaletteColor8>#FFFFE169</PaletteColor8>
  <PaletteColor9>#FF0079CC</PaletteColor9>
  <PaletteColor10>#FFD5D5D5</PaletteColor10>
  <PaletteColor11>#FFFF980F</PaletteColor11>
  <PaletteColor12>#FFDCDCDC</PaletteColor12>
  <PaletteColor13>#FFF5DEB3</PaletteColor13>
  <PaletteColor14>#FF557299</PaletteColor14>
</ColorOptions>