Caleb Jaren, a regular Snort user and contributor has recently put up a blog post about some work he's done for Snort syntax highlighting for the Nano text editor.
If the name sounds familiar on the blog, it's because he recently performed the same work recently with the Notepad++ editor which we lighted back here: http://blog.snort.org/2012/08/snort-syntax-highlighting-and-more-in.html
For his most recent work on Nano check out his post here: http://www.tropismgroup.org/2013/03/07/snort-syntax-highlighting-for-the-nano-text-editor/
