I dunno, personally I think there's something going on with the colored extracts. You're probly right that it's mostly pigments and tannins, but if nothing else they must be lending their own effect somehow.
Callaway's paper "Isolation and Characterization of Yuremamine" shows the proposed structure for the yuremamine molecule (the other alkaloid present in MHRB), which looks like basically a DMT molecule bonded to a tannin. A post on another forum by Dozuki showed his thin-layer chromatographic analysis of an MHRB extract, wherein it was shown that yuremamine degrades under basic conditions into something that is neither DMT nor yuremamine, but a "YDP" as dozuki called it, meaning a Yuremamine Degredation Product.
In Swim's experience, this degredation product is decidedly psychoactive, yet somehow different from DMT. It's basically another part of the mimosa spirit, the yin to n-n's yang, if you will. Swim considers this valuable. He ultimately prefers "full-spectrum" mimosa extract, which is usually orange, that being the unseparated "white" and "jungle" spices.
To remove solvent residue, Swim's friend puts everything in a pitri dish, which is then placed in an empty ceramic crock pot liner, with the crock pot on "high." Leave it for several hours until no solvent smell is left.
The Ultimate Secret of the Universe is that there is no Ultimate Secret of the Universe... there's just a bunch of stuff that happens.