The powder is quite white, but not completely devoid of color. By MS it is very pure.
It actually turns rather dark red, as if I'd blended in a few strawberries. At first I thought it was some weird oxidation reaction going on and was somewhat worried, but after seeing that resveratrol gives a redish cast on dissolution in polar protic solvents, I figure it's the resveratrol. Strictly speaking it could be some contaminant with a very high UV/blue extinction coefficient, I guess, rather than resveratrol.
You know, I have a few grams of completely pure synthetic material (I have samples of just about every bulk product now, it seems [lol]). I'll give that a side by side comparison the next time I blend up some fruit.
I used a household cleaner that contains bleach to clean my kitchen counter, and I noticed a bright red color. I wondered what had happened until I read your post. I suspected there were a few grains of t-res on the counter, even though I hadn't seen any. So I cracked open a capsule of Country Life and tried it. It turns the powder bright blood red! I wondered whether it was the emodin, so I tried AOR t-res. This product can't have much/any emodin, since the capsules are half the size of the Country Life, yet have the same 100mg of t-res. Again, a bright blood red!
Try it yourself!