Noel, for me the contrast between the selected clip background and midi data in that clip is somehow off a bit, hard to explain, but there wasn't enough contrast for me. It's as if the Midi data I was used to seeing was harder to see or somehow didn't look sharp enough, which caused some eye fatigue. And I had no customization of colors going on, just using the new theme as it was displayed upon my update. However, I was able to use a custom slider to increase the contrast a bit and this helps me out, so it's not a problem, really. Keep in mind my eyesight isn't all that great, to be honest, but I never really noticed this as an issue before.
Thanks.