Visibility of the edit Knobs

I'd like to suggest a feature to improve the visibility of the little grey round edit "Knobs" for local adjustments, graduated filters, radial filters, as well as the cloning/healing brush.

I'm on a 27" iMac with a 5K display and I *am* wearing my reading glasses but nevertheless, on many of my more detail-rich images, I find it hard to locate them (I use local adjustments a lot so there may be plenty).

The middle grey they're using now is probably the worst color - if they were bright white, red, green, blue, whatever, it would be much easier to locate them (and when their visibility is set to "Auto" it would still be possible to quickly hide them by dragging the mouse away from the image area).

I could imagine that a way to cycle through the colors of the knobs itself, similar to how it's possible to cycle through the overlay with Shift-O, would be very helpful.

Thanks for considering it.