I've used Krita for years now, and i really enjoy it! I was very excited (and still am) for the new version. I downloaded it and everything went smoothly for the first few minutes. But suddenly, krita apparently decided to let me paint... in the opposite color than the one i selected.
When i select a bright red, i get a bright blue, etc. the overview shows the real colors, however the canvas doesn't seem to match. I didn't mess with the program and just randomly painted a few thumbnails before it happened.
Does anyone know what caused this/how it can be fixed? :/ I really need the program.

A bug in your GPU driver. Depending on your OS, your GPU and if Windows, whether you use Angle or OpenGL for GPU accceleration, swtiching around options might help. You could help us by providing the information from help/system information for bug reports.