Notepad++ is a great text editor and I keep using over and over. I found some GLSL syntax highlight UDL files in the site but they were not up to date and most importantly they we’re not prepared to work with dark themes. So I made two UDLs for GLSL 4.3. One for the default theme and another to use with dark themes. The extensions supported are: vert frag geom tesc tese v f g.
The zip file contains both. To install the themes go to “Language”->”Define your language”. In the “User Defined Language” dialog select import to load the files into notepad++.
Here are some screenshots. Light version with default theme:
Dark version with Monokai theme: