Look into getting Emacs in one of its native OS X incarnations rather than using it in the terminal. Emacs is going to have a lot more options for colors (font locking is the Emacs-speak, I think) in its own app than when it's boxed into a terminal. You also get support for multiple "frames" (windows); Vim can't do this at all and I still miss that from Emacs. I use Linux rather than OS X but if you are parked in Emacs for a long time there's no reason to do it in a terminal. I always used the GTK or the Athena version.