From Jeremy Keeshin:
ColorSearch is an app that lets designers find the exact color they are looking for. It has a simple interface that lets you toggle the amount of red, green, and blue, and then tells you the RGB color in both decimal and hexadecimal.
It's useful, simple, easy to use--and best of all, its free!
Here's a fun game to play with ColorSearch:
In the room you are in, point something out (like Tim's yellow ukulele or Roger's blue sweatshirt). See if your friend can match that color exactly using the RGB sliders. It's surprisingly tricky, but lots of fun!