@kellym0 what do you mean by secondary colour? For a team, lower rank, give me some details.
With black can go a lot of stuff: white dragons for contrast or any light colour you haven't used like soft pink, yeah.
EDIT: sorry, I couldn't resist.
The problem with colour tones, however, is that if you go beyond certain obviously different colours like blue, red, black & white (non-colours), yellow, they (the tones) will not be so easily spotted amongst all the others. Say, pink and orange are close to red.