(Frankly, after the first tasting, I'm not sure why François and Lin made more of that tea, especially if it tasted like butt the first time...)
Serendipitously, François found that the blue colour wasn't as potent as before, while they made the tea at night under indoor lighting; he thought it was because the tea was just old and gross.
The next morning, however, he observed that the blue colour was actually quite strong in the daylight and that the blue colour was not, in fact, drug-induced, and no gremlins had broken in overnight. This, he determined, that it had more to do with the presence of UV light in sunlight and lack of it in household light sources.
And then Google barfed this out when he looked for fluorescent tea: Lignum nephriticum (meaning something like "woody kidneys" (hence its name, kidney wood).
|[Palo azul in the morning light. Photo courtesy of François M. BTW, he is still for hire...]|
(François is now waiting for a UV flashlight he just ordered to confirm his theory...)
(I know I have many excuses for the lapse between posts, and they are numerous but valid and I will fight anyone who complains.)