Easiest 5-star rating ever
I submitted an earlier 4-star rating that basically said "great app; one bug, contacted the developer and there hasn't been time for him to get back to me". Later that same day I got an answer and a solution (my error, not his). Consider this the current review.
With that said, I'd consider this an essential app for web development. Color palette management has always been a series of compromises for me, but no more. If you have any knowledge of basic color theory at all (and even if you don't, truth be told) you'll be pleasantly surprised at what you’re able to do with ease. The WCAG color checking is worth the price of admission right there. I've got a bunch of color apps. This is the one I use.