I'm gonna have to upgrade that thing about color 255.
Did you know, besides not being defined in 999.pal, you can't use color 255 in Larry 6 either? I just made a patch view that adds some splotches in that color to a random easily-seen view and hello what's this then? It came out as transparent! And Larry 6 happens to not have a kernel name vocab.
Indeed, even though Freddy Pharkas' 999.pal does have a pure white 255, it too won't actually show that color outside of system windows, Graph, and text. Anything involving views, which includes background bitmaps, shows nothing for that color, even when the cel's skip color is completely different.
RemapColors was introduced in version 1.001.094. Freddy is .095 and Larry 6 is .113. I'm willing to bet both of them supported color remapping all along, in exchange for that logic error, and simply never used it.