If you use a knob stack instead of a knob/bg then the color will not be visible.
I've done this with round knob stacks, it should work with slider style as well.
Unfortunately you are then left with no indication of what type of automation is active other then the env button.
Default theme/my WIP same settings.
The pan is a stack the vol is not, but I'm using idx to lose the coloring over most of the panel.
Might be why no color on vol slider.
Good luck...