Since updating to 15 I’ve had issues with this kind of text display. This, for instance, is in Messages. Messages itself is set to follow the system theme, and the system theme is set to dark mode. If I set it to light mode the text displays as expected. Trying to manually set the theme in Messages doesn’t fix it. Nothing special going on with the phone itself - it’s a Pixel 6 Pro just running regular Android. Thought I’d post in case anyone has seen something similar.
This often happens on Firefox when the system changes from day to night (light to dark) UI modes whilst the app is open (or open in the background). The app looks like it hasn’t been finished all of a sudden and menus are hard to read.
Force closing and restarting the app seems to kick it back into life. Ultimately it needs better handling from the app to properly listen to the change in system behaviour.