"Brown acid" haha, you know where that comes from don't you? I'm not gonna say I've never taken the stuff because I have but I dont like it, and I used to make a joke about what causes a "bad trip".
Somewhere, some scientist type kook is cooking it up in a cheap hotel's toilet. They start dipping the paper in the liquid to soak it up then hang it to let it dry. Not letting any go to waste eventually a few peices of paper are used to wipe the bowl, including the brownish ring that forms at the water line, giving the paper that particular color and everyone who eats it a "bad trip".
"I'm having a bad trip mannnn"
No, no, that's just the e-coli having a trip of it's own in your acid, man. Tell someone that while having a bad trip and that's when they REALLY flip out.