There is a setting you need to toggle for “unique player colors” instead of team colors. Otherwise you’ll always be blue, teammates always yellow, and enemy always red.
There’s also a hotkey to toggle it in game. I think it’s the Insert key.
Yup, that’s 99% this option. I had the same ‘issue’ for a few games. I’m not sure if I made a mistake or if it was enabled by default (or linked with enabling another thing, by intent or mistake).
Personally, I almost never use this feature, but it should stay and has its uses I’m sure.