Just today I managed to setup my HP Vectra 486 N2 system. System itself is in great condition and works flawlessly with Caldera Dr. DOS 7.03 installed. Problem is that it seems to be running in monochrome only. After running "smonitor c" (modechange tool originally for Trident GPU's) the system reports that the GPU is set to color mode and indeed there are some very light colors visible. You can barely see yellowish and blueish colors but no red or green. Playing around with color saturation, hue and other settings of the monitor didn't do the trick.
For enhanced compatibility I was forced to drill a small hole in the VGA port to allow for standard VGA cables. I did this as carefully as possible. My monitor is atm an all-in-one PC system from 2012 with VGA input.

Any ideas what's wrong here? Another thread here suggests to cut pin 12 of the VGA cable. Has this ever been a proper solution or is it just unproven second-hand knowledge?

CPU: Intel 486 DX2-66
GPU: Cirrus Logic CL-GD5434 (1MB)