The other day I noticed my Windows 11 desktop had a red tint to it. After a bunch of reading and experimenting, I discover that the Windows nightlight feature seems to have permanently altered my colors – even after a shutdown/startup.  To resolve this I ended up doing a ‘full’ shutdown and reboot (by default Windows does a quick shutdown which causes the system to not fully initialize).  If you are having this problem, just do the following:

1. {Shutdown all applications}
2. Open a command prompt (Windows button > type cmd > Click Command Prompt.
3. Type shutdown /r /t 0
4. {Wait for reboot}

Since I kept having problems with this I went ahead and disable night light altogether (Windows button > Night Light) and just installed f.lux instead.