Yeah, painting plastics, especially where there is likely a lot of wear is not a good plan.
As for nail art paint, how long have you seen the nail art last without chipping on nails?
And with the work, the extra prepping materials (degreasing, often priming) you’ll end up spending more money than you would on a set of chroma caps.
As those come in just about any colors, your selection/unique mix of colors will make this a highly personal option too imho.
Finally, get a small LED spot or floof fixture to attach above you shining down on your controller and the knob colors become less important when it comes to visibility.