I feel dumb but I just realized this looks just as good with two colors as it does four. I'll change it right now...
And thanks for the help.
First; this image has 5 colors (a stray dark grey pixel). The bright greys are so similar it makes no point having two colors here. And why dither when you have the darkgrey color it attempts to simulate? Either go with only 2 colors and dither or 3 colors and no dither. I you want a 4th color for the eyes; make it noticable brighter/different.
Like this f.ex: http://i.imgur.com/W6pG6.png
yep :) great readability