Thanks to Jihed over at mac & design (found them at macitt.com) for this customization tip. You can change the color of your OS X dock with these two handy "haxies": Application Enhancer and ClearDock. Both apps are made by Unsanity and distributed for free.
They also offer several other "haxies" that help you customize your mac for anywhere from $10-$20. Some are just for fun like their ShapeShifter themes manager but some are more utilitarian like FontCard and Chat Transcript Manager. Here's what I did to my dock: