Ruminating a bit more, I looked at my histogram code in rawproc. Thing is, the hard-coded R, G and B colors are already maxed out at 255, so I can’t make them any more intense. So, a different shade, maybe? I’d hesitate to take that too far, however, because the red, green and blue histogram colors mean something semantically to the presentation.
I still think changing the contrasting background color might be more productive…