Oh, I hadn't noticed that earlier (I'm oldskool RGB man ;). It seems that "hue" is out of it's limits for many colors and that causes problems for S and V too. If you first tune the H where it should be, then S and V works too. In many cases it seems to be enough to make just one step adjustment to H slider first.

Annoying little bug. I have no idea why it bugs, but it does the same on MorphOS 1.4.5 and 2.0. With Peg1/R7500 here.