White icon turns off the color altogether back to default. Works the same way for accessories etc. Will make it more clear in next UI update.
A color wheel will be added for more distinctive colors. Blonde is much less common statistically (by birth, not dye). Had to choose the most common colors for most nations, far as by-birth colors. Then at least a few dye'd colors for flare. I could only add a few overall within current UI-space.
You'll get a notice when the next update is out, with more UI space for multiple things. Thanks for playing, Lexi!