I find it quite useful to have the colorwheel at hand while painting.
So I just made it fit into the AR picker fromat. I used teh CMYK model to create it, since this model is used for printing. I might create another one using either RGB (according to AR color management) or RYB (traditional painting) models . I might even create one for each one of them.
I chose HS/L over the other modes because luminance is what I like to control most (where I get the widest range of values).
I also created a color sample set for people who would rather use it instead of the picker. But you'll only find pure primary and secondary colors in there (no saturation or luminance variations, nor tertiary colors).
PD: I've been using AR for a few years now (2 or 3), both for professional and personal purposes, and it got the hang of me. Version 3 is a great improvement. Those watercolors are just awesome. Congrats to the AR team. Great job, and thanks! (I hope some day it will be possible to work with CMYK color management, it's the only thing I'm missing right now -but, still, keep it simple!).