You're speaking in the general sense here, so use colouring/flavouring. By adding "-s", you're suggesting that you have a list of some sort in mind - specifically "different typeS of COLOURING". Since we (the readers) have no idea what's on your list, then you should use the general sense: colouring, flavouring.
(Pardon me; I'm using the UK/Aust spellings for these words. Your US spellings are still correct, just keep the style consistent.)