I just got snow white today, doing 3 feeding sessions.

Desert Yellow -> Cream Yellow = 1 Plum
Cream Yellow -> Sylph Green = 1 Plum
Sylph Green -> Snow White = 7 Plums (on the seventh is when i got "growing new feathers" msg)

Just out of curiosity, if i wanted to, how would i go from Snow White to Charcoal Grey