Not entirely sure how to reproduce this, but I grew a mangrove tree and for some reason, some of the leaves turned red, and some of the vines turned purple. I re-logged, and the colors changed slightly but still were discolored. The leaves also appeared pitch black before becoming red. Note that I'm on a somewhat laggy Aternos server, and I'm using FoxyNoTails' Markers Resource Pack, but that should be an issue theoretically.

Edit: I've done some testing and this seems to go away when it begins to rain (or maybe just snow, since this happened in a snow biome). I also took away the resource pack and transported the world to single-player, but the problem still persists, implying that this is neither a server problem, or resource pack problem.