For some reasons I wanted to run Windows 98 SE in VirtualBox.
There are plenty of tutorials how to set this up with Super VGA (1024×768) and many colors, but none of them worked for me.
In particular, the Scitech Display Doctor driver didn’t work with the VBox-VGA virtual hardware, and also the latest UniVBE driver didn’t really like the VBoxVGA adapter. I tried like 20 different setups with the Scitech driver and the latest UniVBE driver in combination with the VBoxVGA, VBoxSVGA and VMVGA driver, but nothing worked.
But finally I found a working setting.
First, I kept the default VBoxVGA adapter in the image’s configuration of the hardware.
Second, I installed a 1024×768 default monitor (important!)
Third, I installed the „old“ UniVBE universal driver (here), release 2008.03.23, manually installing („have disk“) the universal driver from (within the archive) vbemp9x\vbe9x\uni
This finally enabled 1024×768 pixels at 16 bit colors.