For some reason, when I talk to certain people, they say that my text is appearing completely white to them. It's still black on my computer, and appears black to most of my other contacts, but I can't change it for them. Is there a way to fix this? It seems mostly to happen when I talk to people on mobile versions or web messengers, or other multimessenger programs.

Many clients support overriding contacts' fonts. maybe your contacts are doing that with you, and they don't realise it.