So after using this awhile i've spotted one problem. After picking a color i have to click back into the drawing window before i can paint again, causing a useless stroke and the pressing of my undo hotkey. I'm in windowed mode or w/e you call it using cs5.
I second the multiple interface coloring for CS6. Can I also mention a bug? When photoshop is not focused and you mouse over the Coolorus interface, it steals focus back to photoshop. This isn't really good, and you should definitely fix it as it's very annoying. Also, I like the extra effort that's gone into the graphics of the color wheel. Cheers!
Things I wish it had: Visual feedback showing the new color compared to the previous color. This could come in a few ways.
1. Swatches next to each other like the classic color picker.
2. Leaving a "dot" behind on mousedown, to show the previous saturation and value, and having it disappear on mouseup. Something similar could be done when shifting hue.
3. Showing a comparison of the the actual RGB/HSV values.
Re-sizable color wheel
Not much to say here, other than one thing that always bugged me about PaintersWheel was that it's stuck at a constant size. It looks like this one will be more complicated to implement in yours, if you want all the buttons to stay the same size.