Parallels 17 colors and game performance on iMac M1

Having read the hype about the new iMac with Apple Silicon, I bought an iMac M1(2021) 24" 16GB/256GB and installed Parallels 17 plus Windows 11. Purpose: to be able to continue running the flight simulator X-Plane 11. Result: the combo is easy to install and does not crash, which is admirable.
However, even with minimum graphics settings in X-Plane I get warnings about low frame rate and the colors on the screen are weird. The mountains are light blue and the aircrafts give a sharp black shadow although the sky is midnight black. Questions to clarify before I go from Trial to Purchase:
1. I understand that X-Plane is a heavy load on graphics but some X-Plane fans seem to be quite enthusiastic about the performance they get on their iMacs with M1 so I wonder if there is something I can improve by changing the Parallels/Windows settings?
2. In the Parallels forum people seem to have been able to get correct colors by changing the handling of "gamma". Can you please explain how this should be done in Parallels 17?