Forcing video to NTSC (or leaving it as Disc of course) results in a black and white image, no matter if i turn on patch video or patched MIOS.
Forcing PAL (either 50 or 60) with patch video On (normal) will give a freeze on a green screen right after the GC loader screen. However, I tried the patched MIOS option and with it both PAL50 and 60 produce full color picture (with patch video still set to normal). Your patched MIOS suggestion was right on the money!
I tried setting patched MIOS to No once and, as expected, it freezed on the green screen again so I guess that confirms it (when forcing NTSC video it gives the black and white picture either with patched MIOS or not). Am I correct in assuming that, when set to auto, patched MIOS should be turned on when trying to force PAL video on a NTSC game when running on a PAL Wii? Especially since it's one of those settings that are not saved in the configurations and keeps defaulting to auto whenever you restart NeoGamma.
Oh, I tried setting the Wii to 50 and 60Hz modes, they both produce exactly the same results in NeoGamma (haven't tried Wiigator's, didn't see the need), and I remember from testing this afternoon that Wiigator's produces the green screen freeze when pressing X and L (the PAL options), everything else produces color images, except for R, the 480p option, that doesn't work as expected, and it's a multi game disc, but I guess none of this matters anymore.
This will be completely unrelated, but while I'm at it, could I perhaps make a small suggestion, when loading a multi game disc, if the name of the game is too big it will get cut short by the screen, and when selecting the second game of a two game disc you won't be able to see if it actually is selected or not. Perhaps centering it in the screen like you do with loading Wii games from USB, or at least text wrapping it to a new line would be good. But this is merely an aesthetic suggestion, obviously everyone can work fine with it as it is, and you could always argue that I should give my games smaller names when making multi game discs
EDIT: I failed to mention but I think it should be obvious, this is all Gamecube stuff related by the way...