This issue only happened to me while editing an archived project.

Oh, I see. Yeah it's frustrating. It seems the current situation is "Archived Projects should not enforce a red color".

Interestingly, I think this is a feature that automatically marks Archived projects as red ones.

I've updated the description.
This isn't about colors; there's a drop-down in Project called "color", and editing sometimes changes the value of that field.

This is interesting but note that calculating a suitable background/text contrast is a weird complex separate science and I'm not sure about how to implement this for any generic color