Why is mdma sometimes white and sometimes brown?

Yes. Lou Bel is correct. There is a phase near the end of the synthesis where chemists could “wash” the MDMA of the impurities. This is often skipped. The marketplace is very confused as well. read more

This is due to the purity of the mdma. Pure mdma is white/grey/pink-ish while the less pure it is the more brown it becomes. This is due to lazy or incompetent chemists. read more

MDMA in its purest form is a white (sometimes slightly off-white), crystalline substance which can be pulverized into a powder (just a lot of smaller crystals, really, but it looks like powder at this point). Sometimes MDMA can be red/brown, or sometimes it can be a more yellow color. read more

I don’t know much about it’s synthesis, but I know that purifying low quantities of tan MDMA (which is usually 75–85% pure) is rather wasteful, since a certain amount of the drug will also be lost. read more