When monitor is connected via hdmi I get wrong colors. This appears during boot
before the gui (x.org) gets started (frame buffer boot animation). Wrong colors
(sort of violet instead of black) also appear on frame buffer text console and
with x.org gui.
This bug appears with and without "amdgpu.dc=1" kernel parameter.
While running x.org I've turned the monitor off and on again. This gives
correct colors but the screen resolution goes to 1024x768. So it's no work
around.

The bug does not occur if the monitor is connected via dvi.

System:
Kernel 4.15.4
openSuse 42.3