Here is a little script that highlights multiple egrep search terms in different colors. It pipes multiple greps together. Be careful, if you give it a search term that happens to match the escape sequences for ANSI color, you might get unexpected results.
There are a number of tools that already do this: ack, ccze. This just needs bash (maybe even other shells) and grep. I was aiming for portability; no need for compiling, perl, ruby, python, <insert runtime here>. Got the idea here.