Do I first uninstall Renoise 3.0 and then reinstall the new 3.1? Or is there just an update patch I apply? How do I turn off all the red highlights? I like the plain black/grey look.
I’m pretty sure 3.0 and 3.1 have their own folders, so you can install them both at the same time if you like.
Have a look at the different themes available in Preferences/Themes.
I’d keep them both side by side, it doesn’t take much space on your drive. They are bundled with different resources that might come in handy and if you run into a backwards compatibility issue you can switch between the versions.
So just install it the regular way and it won’t mess with the previous versions.