What color should the reagent be?? IF it's brown does that mean that the test is unreliable?? A pill I tested with a brown reagent went purple/black after 15 sec. What can be assumed??
well you have one of little testers in the plastic tube right? well if so then the brown colour comes from the reagent reacting with the plastic. thats why the new big ones are in a glass container. the big ones wont go brown. the small ones are no longer sold,, but there's still a few around oz.
the chemical still works exactly the same when its brown, its just harder to see the reaction. so your black/purple reaction is a classic MDMA result.
if you arent sure then invest in a big one, it will be well worth it.