I have played around and add "convert -modulate value1, value2, hue input output" (not released). And also some other stuff will be follow next. If you have more like this tell me.
I thinked about it at the beginning too, but i stop do this for the moment, because i does not now, in all parts, how does the range for the values. I have also the problem that i does not can make values to select with a point insite, like for the "hue" function. A real time view will be hard work i think, because it will slow down the process (yab is a script language).
The output image changes up to minus 0.02 KiB, so it does anything. But i have seen that this function will be used to "-separate" colors. I will see and learn.