The color picker in OS X isn't half bad but, unfortunately, it isn't offered as a stand alone utility. That's easily remedied with some simple instructions and even more easily remedied by downloading the fruits of those instructions which you can drop into Applications/Utilities where it'll live happily alongside DigitalColor Meter.
[update] A nice compliment to the color picker is the Developer Color Picker created by Wade Cosgrove over at Panic.