Ion Tokens as Green Maneuver?
All I can spot in the rules ATM which most closely looks like what you said is about 2 cards saying conflicting things about using an ability and forbidding the ability. The forbidding card takes priority. This case isn't about forbidding something, however. White is not a color that forbids green. So I think the case was in fact not covered by the basic rules and a FAQ ruling inserts a new piece of clarification.
The White-1 maneuver isn't 'overriding' any color choice. Think of the maneuver as if you selected it from your dial, nothing else special.
Consider this: if you had an effect that said "Treat all straight maneuvers as white" and Nunb's "Treat all straight maneuvers as green" then the imaginary 'all white' would take precedence because of the rule you're thinking of. This is also why there was errata on Daredevil I believe (so you couldn't overwrite the color, and you'd be forced to take a stress).
This is also why there was errata on Daredevil I believe (so you couldn't overwrite the color, and you'd be forced to take a stress).
You can still change the color of Daredevil's maneuver, but gaining the stress is now explicit so you won't be able to avoid it.
Mu0n and mege have the issue covered, though.