Here's a first go at my "concept", using standard Avery color-coding sticker dots (1/4"). The dots stick well...when they don't overlap the white marker ridge.
I tried sticking the dot off-center, below the marker: it sticks very well...but doesn't look good. Next option: punching out the top of the dot to clear the ridge (as seen in the ladder filter cutoff pot).
Again, good stick...but not ideal looking. If I could find a small rectangular punch (2mm), that would look better. Oh well...too much time on my hands, I guess...
At the very least, it's a quick way to test color schemes, if I ever decide to purchase color knobs. BTW, no need to add color to all the knobs, imho, but only to contrast sections. I am thinking light grey for the audio mod section.