Colorblind Assistant is a very basic color picker, with one important twist: It gives each color a human-readable name. So I can place my mouse cursor over a recent PCWorld magazine cover displayed on my screen, and be able to say in confidence that it is a deep sky blue, and not light pink (as it appears to me). If I'm talking to someone on the phone or writing an email message about color picks for a design, I can now say that a design element is orange without fear that it is actually green.
Colorblind Assistant can be useful even if you aren't color blind: Applications such as change the screen's color temperature to suit the time of day, so Colorblind Assistant can come in handy if you just want to make sure that the red you're seeing is really red, without disabling F.lux.
The human-readable names that Colorblind Assistant picks aren't always names I would use in conversation, but they steer me in the right direction. I may not tell someone that I want a logo in "Fire Brick Red," but I may use something like "deep red" (and not "dark brown"). Apart from those names, Colorblind Assistant also shows RGB values, brightness, saturation, and Hex color codes.
Colorblind Assistant is strictly a one-trick pony. If you're looking for a powerful color picker and you aren't color blind, you'll be much better off with the excellent , which also lets you save color swatches for later reference. But for color-blind users, being able to put names to colors is an invaluable feature--I can only wish for a smartphone app that did the same thing.
Note: Colorblind Assistant is free, but the author accepts donations. The download button takes you to the vendor's site, where you can download the latest version of the software.