A while ago I wrote about a colour theme problem specific to OS X. Thankfully in Emacs 24.4 the OS X (a.k.a. NS) port of Emacs uses sRGB colours by default (at least on OS X Lion (10.7) and newer), so you’ll no longer need to install Emacs from homebrew (or apply an sRGB colour support patch manually). If for some reason you want to stick to the colours add this to your Emacs config:

(setq ns-use-srgb-colorspace nil)

I doubt that anyone would want to do that, but the option is there for those of you who want it.