Thanks for playing!
Red/Blue is indeed the most consistent at the moment, but there will be meta unlocks that will change the plums to some other dual-color symbol randomly so it won't be the same every run.
I got Yellow to work many times when I got an early (deal 10% of your chips as damage) or (deal damage equal to the amount of your yellows/2) but otherwise yeah, it's probably not good enough. Leprechaun might get degraded from boss to elite in the future to prevent yellow runs from getting ended by him unavoidably