All those shades of gray are producing an optical illusion of sorts, but one without sufficient depth. It's not a good scheme.
I was not seeing an (in retrospect obvious) color difference that was disappearing into the chrome. And without that, it became indecipherable.
But in my defense
in fact, there's one color difference too many: why would "not in key" have different conventions for black keys and for white keys? There are now two different "not in key" colors/tints/treatments that need to be read -- or completely ignored -- in order to make fast sense of the piano roll. In keys with 2 or more accidentals it gets especially weird.
But now that I see it, I see it. There's still an optical illusion to it, but it's no longer a total WTF.
But WTF, it really should be better. Wouldn't take much.
I tried seeing if it was tweakable in the theme config window, but none of the obvious things made a difference, and my eyes soon glazed over.
But that's Reaper.