What color should burnt marijuana ash be?

I have been told that good hash will leave white ash and crapier stuff leaves black ash. Is this true with buds too? I have noticed a burnt bowl of crappy weed will sometimes stay black, maybe from not being flushed correctly or whatever. Any insight?

blue.......but then again, i do buy my bud from smurfs.

Better the bud the more white the ash will be.