If you are interested in a free and simple color picker which works for MAC OSX and Windows platform please look at http://www.m2port.com/
It displays data of Rec 709 YCbCr and fixes pixel location where you like to read color changes - you see changes during color grading at defined position.
Tip for MAC: take care about huge shadow around Windows, this acts like a filter if you pick close by
It looks like you're new here. If you want to get involved, click one of these buttons!