Just coffee and regular tea so far. Results ranged from pretty good on fiber paper to a sickly piss-yellow on RC paper.
I plan to try some Red Zinger tea next since I don't like to drink the stuff - it's a pretty color, tho'.
I'll try to remember to report back with my results.
BTW, there are theories that the tannic acid in tea can harden and protect the emulsion against damage so it's doing more than simply coloring the print.