I'm stupid. :/
I looked all over. Tried changing all the possibly relevant colors in the System colors menu. Even changed the "Letter" setting about a million times. All the other texts changed color, but the tags remained black. I gave it one more go, and realized that if I change the "Letter" color, the existing tags don't automatically change color. All new tags, however, do.
I could swear I've tried this before, but apparently not. Problem solved.
