Hello guys, I'm trying to run games in 720p on my 1080p monitor, but when I change its resolution to 720p the colors become very saturated with high contrast. Every higher resolution until 1080p works perfect. It is funny because if I take a screenshot the colors look normal, that's why I took photos of my monitor.
It may have more to do with your particular monitor. Have you tried a different input on you monitor. It would require a different cable too, but if you are using DVI, try HDMI, or Visa Versa.
But why does other resolutions slightly higher (and with different proportions) work perfectly?
They don't. They just look less blurry. The lower the resolution you go, the more it works to downscale, and the worse it looks. This is a downside of CRT's. They have fixed pixels, and therefor don't look as good at anything but their native resolution. Also, part of the quality is related to the chip in your monitor dealing with the downscaling. You could see if using Nvidia's scaler in the control panel is any better, but it won't be good any way you look at it.