I notice that over time, keyboards (for a standard x86 box) started as two-tone greys, made a brief stop at solid white/beige, and ended up at solid black. The second change was clearly "to match the black PC and monitor", and the first one was likely an economization feature...
I'm curious if anyone has studied the effect of going with different colour pairs, or solid colour caps, on performance? I always figured two-tone caps offered some minor benefit for locating where the user is, especially when dealing with the low-traffic sections of the board, like the function row and number pad.