Solarized (Dark) syntax highlighting for Pandoc/Markdown in Notepad++ (add this to userDefineLang.xml); can't recall which source file I modified... happy to give credit!

gistfile1.xml

<NotepadPlus>
    <UserLang name="Markdown" ext="markdown mdown mkdn mdwn mkd md Rmd" udlVersion="2.1">
        <Settings>
            <Global caseIgnored="yes" allowFoldOfComments="no" foldCompact="no" forcePureLC="2" decimalSeparator="0" />
            <Prefix Keywords1="yes" Keywords2="yes" Keywords3="no" Keywords4="yes" Keywords5="no" Keywords6="no" Keywords7="no" Keywords8="no" />
        </Settings>
        <KeywordLists>
            <Keywords name="Comments">00# 00## 00### 00#### 00##### 00###### 01 02 03[ 03![ 03&lt;!-- 04] 04] 04--&gt;</Keywords>
            <Keywords name="Numbers, prefix1"></Keywords>
            <Keywords name="Numbers, prefix2"></Keywords>
            <Keywords name="Numbers, extras1"></Keywords>
            <Keywords name="Numbers, extras2"></Keywords>
            <Keywords name="Numbers, suffix1">.</Keywords>
            <Keywords name="Numbers, suffix2"></Keywords>
            <Keywords name="Numbers, range"></Keywords>
            <Keywords name="Operators1"></Keywords>
            <Keywords name="Operators2"></Keywords>
            <Keywords name="Folders in code1, open"></Keywords>
            <Keywords name="Folders in code1, middle"></Keywords>
            <Keywords name="Folders in code1, close"></Keywords>
            <Keywords name="Folders in code2, open"></Keywords>
            <Keywords name="Folders in code2, middle"></Keywords>
            <Keywords name="Folders in code2, close"></Keywords>
            <Keywords name="Folders in comment, open"></Keywords>
            <Keywords name="Folders in comment, middle"></Keywords>
            <Keywords name="Folders in comment, close"></Keywords>
            <Keywords name="Keywords1">http:// https:// (http:// (https:// (/ &lt;http:// &lt;https://</Keywords>
            <Keywords name="Keywords2">--- ===</Keywords>
            <Keywords name="Keywords3">- + &gt;</Keywords>
            <Keywords name="Keywords4">*</Keywords>
            <Keywords name="Keywords5"></Keywords>
            <Keywords name="Keywords6"></Keywords>
            <Keywords name="Keywords7"></Keywords>
            <Keywords name="Keywords8"></Keywords>
            <Keywords name="Delimiters">00` 01\ 02` 03[ 04\ 05] 06** 07\ 08** 09__ 10\ 11__ 13\ 15 16 17 18 19 20 21 22 23</Keywords>
        </KeywordLists>
        <Styles>
            <WordsStyle name="DEFAULT" fgColor="839496" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="COMMENTS" fgColor="b58900" bgColor="002B36" fontName="" fontStyle="1" nesting="0" />
            <WordsStyle name="LINE COMMENTS" fgColor="586E75" bgColor="002B36" fontName="" fontStyle="1" nesting="9247" />
            <WordsStyle name="NUMBERS" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS1" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS2" fgColor="586E75" bgColor="002B36" fontName="" fontStyle="1" nesting="0" />
            <WordsStyle name="KEYWORDS3" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS4" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="2" nesting="0" />
            <WordsStyle name="KEYWORDS5" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS6" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS7" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="KEYWORDS8" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="OPERATORS" fgColor="0000FF" bgColor="002B36" fontName="" fontStyle="1" nesting="0" />
            <WordsStyle name="FOLDER IN CODE1" fgColor="F8F8F8" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="FOLDER IN CODE2" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="FOLDER IN COMMENT" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="DELIMITERS1" fgColor="79089C" bgColor="002B36" fontName="Courier New" fontStyle="0" nesting="0" />
            <WordsStyle name="DELIMITERS2" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="1" nesting="0" />
            <WordsStyle name="DELIMITERS3" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="1" nesting="9243" />
            <WordsStyle name="DELIMITERS4" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="1" nesting="9239" />
            <WordsStyle name="DELIMITERS5" fgColor="2AA198" bgColor="002B36" fontName="" fontStyle="2" nesting="9231" />
            <WordsStyle name="DELIMITERS6" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="DELIMITERS7" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
            <WordsStyle name="DELIMITERS8" fgColor="6C71C4" bgColor="002B36" fontName="" fontStyle="0" nesting="0" />
        </Styles>
    </UserLang>
</NotepadPlus>