Color Suite is a ridiculously comprehensive color-identification app with an easy sampling tool and a wealth of information. Just point the little dot at the color you want to identify, and it’ll tell you pretty much everything about it, including its complementary color, how it appears to eight different kinds of color-blindness, and even which Crayola is most similar.
It actually has an insanely long list of products you can match, like several brands of house paints, colored pencils, and make-up.
So basically, if you see a color, you can use that color for everything. This app really, really wants you to do that.