With GDB you can use all of the glory that is printf, inside of the termal. This means terminal control codes, that you can use to change colors on the screen for syntax highlighting.

peda is an excellent project that uses this to great success: https://github.com/longld/peda

All of that being said... it's really not very practical. (: But, it CAN be done, and it is done, I'm just glad I'm not the person doing it.