You might try httpstergeek's Notepad++ defined language file.
Note that Splunk Enterprise 6.5 includes syntax highlighting for searches, see Help reading searches in the Search Manual.
Related (putting it here in case someone finds this answer looking for .conf file syntax highlighting): Yorokobi's vim extension.
unable to install in Notepad++
saw a similar note on stackflow
I'm aware of 6.5 highlighting scheme, thats what I'm trying to emulate in Notepad++
A quick google search turned up these sublime packages in case they have been overlooked by anyone, I personally haven't used them. I am on the hunt for something similar in atom.io as well though.