Hey, if you guys want to change the palette of the waves/coins/flying fartblasters: the byte in ROM that specifically determines which palette is used for Dark Wave is 1480C in ROM (2C80C in LoROM if you wanna fiddle live in Geiger's).
A few choices that I've found seem particularly conducive to coin color are 07, 11 and 15, but I'm sure there are others. These are the same palettes used by spells and (I think) weapons, so best not to mess with the palettes themselves, lest you suffer the consequences, but 1480C dictates which one is used by this command specifically, so have at it!