My customized version of the Transparent Blue TaskPaper theme. Original is at https://github.com/dataduke/mac-taskpaper/blob/master/Themes/Transparent%20Blue.taskpapertheme

TransparentBlue.taskpapertheme

<theme>
  
  <!-- Window Style -->
  <color alpha="1.0" blue="0.99" green="0.80" id="foreground" red="0.59"/>
  <color alpha=".95" blue=".1" green=".1" id="background" red=".1"/>
  <window backgroundColorID="background" foregroundColorID="foreground" shouldUseHUDScrollers="yes"/>
  
  <!-- Text View Style -->
  <color alpha="1.0" blue=".48" green=".48" id="tag" red=".48"/>
  <color extendsColorID="foreground" id="handle"/>
  <color alpha="1.0" blue=".4" green=".4" id="insertionPoint" red=".4"/>
  <color alpha="1.0" blue=".2" green=".2" id="selection" red=".2"/>
  <font id="base" name="Helvetica Neue" size="12"/>
  <characterStyle fontID="base" foregroundColorID="foreground" id="base"/>
  <paragraphStyle alignment="NSLeftTextAlignment" id="base" lineHeightMultiple="1.0" lineSpacing="0" paragraphSpacing="4" paragraphSpacingBefore="0"/>
  <textView defaultCharacterStyleID="base" handleColorID="handle" insertionPointColorID="insertionPoint" selectionColorID="selection" shouldAntialiasText="yes" shouldShowNoteHandles="no" shouldShowProjectHandles="yes" tagColorID="tag"/>

  <!-- Task style. This section defines the styles that are applied to task lines. -->
  <color alpha="1.0" blue=".85" green=".85" id="task" red=".85"/>
  <font extendsFontID="base" id="task"/>
  <characterStyle fontID="task" foregroundColorID="task" id="task"/>
  <entryRule lineCharacterStyleID="task" matchesQuery="type = task" paragraphStyleID="base"/>

  <!-- Note style. This section defines the styles that are applied to note lines. -->
  <color alpha="1.0" blue=".6" green=".6" id="note" red=".6"/>
  <font extendsFontID="base" id="note"/>
  <characterStyle fontID="note" foregroundColorID="note" id="note"/>
  <entryRule lineCharacterStyleID="note" matchesQuery="type = note" paragraphStyleID="base"/>

  <!-- GroupHeader style. This section defines the styles that are applied to groupHeader lines. (top level projects) -->
  <color extendsColorID="foreground" id="groupHeader"/>
  <font id="groupHeader" name="Helvetica Neue Light" size="16"/>
  <characterStyle fontID="groupHeader" foregroundColorID="groupHeader" id="groupHeader"/>
  <paragraphStyle extendsParagraphStyleID="base" id="groupHeader" paragraphSpacing="7" paragraphSpacingBefore="12"/>
  <entryRule lineCharacterStyleID="groupHeader" matchesQuery="isgroupheader" paragraphStyleID="groupHeader"/>

  <!-- @done -->
  <color alpha="1.0" blue=".3" green=".3" id="done" red=".3"/>
  <characterStyle foregroundColorID="done" id="done" strikethroughStyle="NSUnderlineStyleSingle"/>
  <entryRule contentCharacterStyleID="done" matchesQuery="@done"/>

  <!-- @focus and project contains focus -->
  <color alpha="1.0" blue="0.18" green="0.50" id="focus" red="1"/>
  <characterStyle fontID="base" foregroundColorID="focus" id="focus"/>
  <entryRule lineCharacterStyleID="focus" matchesQuery="(project contains focus or @focus) and not @done"/>

  <!-- @high -->
  <color alpha="1.0" blue="0.65" green="0.82" id="priority" red="1.0"/>
  <characterStyle fontID="base" foregroundColorID="priority" id="priority"/>
  <entryRule lineCharacterStyleID="priority" matchesQuery="@high and not @done"/>

  <!-- @next -->
  <color alpha="1.0" blue="1" green="1.0" id="next" red="1"/>
  <characterStyle fontID="next" foregroundColorID="next" id="next"/>
  <entryRule lineCharacterStyleID="next" matchesQuery="@next and not @done"/>

  <!-- @today -->
  <color alpha="1.0" blue="0.38" green="1.0" id="today" red="0.66"/>
  <characterStyle fontID="today" foregroundColorID="today" id="today"/>
  <entryRule lineCharacterStyleID="today" matchesQuery="@today and not @done"/>

  <!-- @overdue -->
  <color alpha="1.0" blue="0.99" green="0.45" id="overdue" red="1.0"/>
  <characterStyle fontID="overdue" foregroundColorID="overdue" id="overdue"/>
  <entryRule lineCharacterStyleID="overdue" matchesQuery="@overdue and not @done"/>

  <!-- @someday -->
  <color alpha="1.0" blue="0.40" green="0.40" id="someday" red="0.40"/>
  <characterStyle fontID="base" foregroundColorID="someday" id="someday"/>
  <entryRule lineCharacterStyleID="someday" matchesQuery="@someday and not @done"/>
  
  <!-- Project style. This section defines the styles that are applied to project lines. -->
  <color alpha="1.0" blue=".99" green="0.77" id="project" red="0.78"/>
  <characterStyle fontID="groupHeader" foregroundColorID="groupHeader" id="project"/>
  <paragraphStyle extendsParagraphStyleID="base" id="project" paragraphSpacing="4" paragraphSpacingBefore="10"/>
  <entryRule lineCharacterStyleID="project" matchesQuery="type = &quot;project&quot;" paragraphStyleID="project"/>
</theme>