Im almost 100% sure that any "big" hit, and I mean a BIG hit, turns yellow. Bongs or G-bongs are the best place to see it. My reasoning is that I havew a buddy who always used to make me take fat rips. it was when iw as younger. Anyway we would have some real good weed. And if still took a big hit it just turned cream yellow

So I'm pretty sure a yell smoke cloud ( at least while still in the bong, not while exhaling) If its yellow thats good.