Due to all 8 of the sprite palettes lines being used in his screen, Funky's surfboard has to share its palette with something, so the devs chose Dixie's palette.
It wasn't always intended to be like this, though, as an unused palette matches up with Funky's higher-res render for the game. More details can be found in
this post of mine in my 'Unused Content in DKC Trilogy' topic.