Noticed today that it seems black combos do not have a hitlightning displayed - I don't know whether that was the case before but I don't really feel like anything has changed really, so I'll be leaving this here.
As you can see on the first image below there are leftovers from the orange combo before, so that's checked and working; no problems with any colours but black.
Examples:
Given that these are old maps I tried it out on newer ones by setting one combo colour to absolute black (the very bottom left preset one in the RGB window) and naturally, the same thing happened, so that's not a thing about old .osu data either.
As you can see on the first image below there are leftovers from the orange combo before, so that's checked and working; no problems with any colours but black.
Examples:
Given that these are old maps I tried it out on newer ones by setting one combo colour to absolute black (the very bottom left preset one in the RGB window) and naturally, the same thing happened, so that's not a thing about old .osu data either.