This is a two page extract that covers the basics, might need to run it past the Forum Moderators incase of any particulars pertaining to copyright infringement.
Basically COLOUR assign colour to an index.
COLOUR Index, $RGB the index being the colour register you point to and the $RGB the value.
So I guess you could create a simple FOR /TO NEXT LOOP with an $RGB string value to manipulate individual registers.
PALETTE allows you to install a whole palette in a singLe statement:
PALETTE 0,$F00,$0F0