[pmr_]

I use different .Xdefaults for my shell "styling" and are incredibly happy with it. Changing to another theme is just one xrdb -merge away.

[gcb]

this goes a little further i guess. you can add color to regexp matches for command outputs.

[pmr_]

Apparently. Judging from what it does the implementation could be a nice example of layering shell tools on top of each other to get new functionality. Probably it has some uses for people that work entirely with the shell.