GBC does it with quite a few games (I used to have all the palettes at the PocketHaven forums, but they might be lost now?)
Fortunately, these at least are documented on TCRF's GBC bootROM article
Incidentally, I just managed to nop over the branch past the Game Boy Player palette switch in Super Mario Advance 4, so I've submitted a patch to RHDN for it. Fingers crossed. Obviously, the difference is minor, but I figure the palette is there, we might as well take advantage of it. EDIT2:
Approved, link to patch
I finally got around to doing the same for Mario & Luigi. There's a cmp
, followed by a bne
the branch to have the game run in GBP mode.
Lay users: with a hex editor, go to 0x0001A4FC
in the (USA) Mario & Luigi ROM, where you'll find 0x18D1
. Replace these two bytes with 0xC046
. Should be easy enough to do for other regions, too, if it's not at the same address just search for a few nearby bytes.
I'm not going to bother submitting this one to RHDN because it's not a true palette that this enables; rather, the GBA version has the "true" palette and GBP-mode just dims it across the board—that is, anything that was white is now gray, etc. Any decent emulator can probably do a better job improving the picture than this lazy "fix".