This issue for the presence of syntax highlighting is actually a shameless plug for my library for doing exactly that: https://github.com/trishume/syntect
If syntect doesn't fit your highlighting needs let me know, I might be able to adapt it to work for you.
It's a long way to go from now to integrate syntax highlighting because I am rewriting whole program from scratch, anyway I'll definitely consider your library.
This issue for the presence of syntax highlighting is actually a shameless plug for my library for doing exactly that: https://github.com/trishume/syntect
If syntect doesn't fit your highlighting needs let me know, I might be able to adapt it to work for you.