Macbook screen red hue, increased brightness and shadowing of other screens seen in the background

My MacBook has suddenly change the display and now has red hue, increased brightness and shadowing of other screens seen in the background (to the extent that I can read the text of other web pages if i have multiple internet windows open, or I can read the words/see other programs running behind the active screen). It seems to then retain this info as a kind of shadow, so even if i minimise the screen it is still there. lAst update was macOS Catalina 10.15.7. I've tried rebooting it with no improvement.

Anyone have any suggestions/fixes? I have an exam in 2 weeks, and really need to be able to use this effectively.

Thanks!