I've had brown, beige, off white and white give the desired results in both experience and reagent reactions. I'm no chemist, I don't know why it can vary so much in color/texture (I've also had it as a very fine powder and more often it's crystalline and kind of sparkles) but that seems to be the way it is. Likewise, anything with any of the above appearances could easily be something else too so like everyone the others are saying just test the stuff if you've got any doubt and even if you don't - just to be safe