Julia language syntax highlighting for Notepad++. Goes in /users/{username}/AppData/Roaming/Notepad++.

julia_npp.xml

<NotepadPlus>
    <UserLang name="Julia" ext="jl">
        <Settings>
            <Global caseIgnored="no" />
            <TreatAsSymbol comment="no" commentLine="yes" />
            <Prefix words1="no" words2="no" words3="no" words4="no" />
        </Settings>
        <KeywordLists>
            <Keywords name="Delimiters">&quot;00&quot;00</Keywords>
            <Keywords name="Folder+">begin function type for while if</Keywords>
            <Keywords name="Folder-">end</Keywords>
            <Keywords name="Operators">&apos; - ! &quot; $ % &amp; * , . / : ; ? @ \ ^ _ ` | ~ + &lt; = &gt;</Keywords>
            <Keywords name="Comment"> 1 2 0#</Keywords>
            <Keywords name="Words1">abstract and begin break case catch const continue do else elseif end false for function global if in let local macro module new next not or quote rescue return then true try type unless when while </Keywords>
            <Keywords name="Words2"></Keywords>
            <Keywords name="Words3"></Keywords>
            <Keywords name="Words4"></Keywords>
        </KeywordLists>
        <Styles>
            <WordsStyle name="DEFAULT" styleID="11" fgColor="000000" bgColor="FFFFFF" fontName="Lucida Console" fontStyle="0" fontSize="9" />
            <WordsStyle name="FOLDEROPEN" styleID="12" fgColor="008000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="FOLDERCLOSE" styleID="13" fgColor="008000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="KEYWORD1" styleID="5" fgColor="0080C0" bgColor="FFFFFF" fontName="Lucida Console" fontStyle="0" fontSize="9" />
            <WordsStyle name="KEYWORD2" styleID="6" fgColor="000000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="KEYWORD3" styleID="7" fgColor="000000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="KEYWORD4" styleID="8" fgColor="000000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="COMMENT" styleID="1" fgColor="ADADAD" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="COMMENT LINE" styleID="2" fgColor="C0C0C0" bgColor="FFFFFF" fontName="Lucida Console" fontStyle="0" fontSize="9" />
            <WordsStyle name="NUMBER" styleID="4" fgColor="000080" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="OPERATOR" styleID="10" fgColor="0080C0" bgColor="FFFFFF" fontName="Lucida Console" fontStyle="0" fontSize="9" />
            <WordsStyle name="DELIMINER1" styleID="14" fgColor="808040" bgColor="FFFFFF" fontName="Lucida Console" fontStyle="0" />
            <WordsStyle name="DELIMINER2" styleID="15" fgColor="000000" bgColor="FFFFFF" fontStyle="0" />
            <WordsStyle name="DELIMINER3" styleID="16" fgColor="000000" bgColor="FFFFFF" fontStyle="0" />
        </Styles>
    </UserLang>
</NotepadPlus>

In my old version of Notepad++ (5.7, from 2010), the import command seemed to be View/User-Defined Dialogue...

Also, I found it helpful to remove the "fontName" and "fontSize" values, since they overrode my custom defaults.

Feel free to contribute to https://github.com/JuliaEditorSupport/julia-NotepadPlusPlus
JuliaEditorSupport is an organization that hosts julia extensions for various text editors and IDEs.