Set 4: Tryptamines
Tryptamines are very unlikely adulterants, with the possible exception of (the rather useless) 5-MeO-DALT; they are expensive and of somewhat limited availability.
Marquis - slight yellow
Mecke - Red/Brown
Mandellin - yellow
Thought this might be helpfull i have Marquis tested two seperate batches of sold as 5-Meo-DALT in the U.K. and both reactions were simalar but different to your results.
Reagent was purchased approx 5 weeks ago 5-Meo-DALT about a month old (very active @35mg Oral), a different fresh batch tested a little lighter in colour but definatly brown more than yellow, both medium/speed reactions picture was taken after 3-5mins.
test was done by adding a small amount to the drop of reagent that initialy floated then sank into the droplet of reagent going yellow/brown then darkening.
hope this is of some use!
Stay safe peep's