virtualbox.org

Since about 6.x I've had problems reading the VirtualBox Managers screen - basically the color scheme appears to be white on white (see attached image). I can't find where the colors are defined or even which colors VirtualBox Manager is using. Normally it's not much of a issue but I can't read the error message I'm getting now (see bottom of attachment)

I'm using the latest version of Fedora 33.

I've a suspicion this will have something to do with a Qt configuration on your host OS, though I have no idea where to look.

VirtualBox 6.1.x (and earlier) simply does not support dark mode. Some GUI elements use the system colors, some use fixed colors, and the latter are not configurable.