This could be an issue that started with Windows 10's 1903 update from last year. The two links below seem to describe the same thing you're experiencing right now (color banding with an NVIDIA card after a recent Windows 10 update) and both offer the same step-by-step solution that could be worth trying:
* https://windowsreport.com/nvidia-color-banding-fix/ (How to fix Nvidia color banding issues on Windows 10 PCs)
* https://www.reddit.com/r/nvidia/comments/c6dfkt/fixworkaround_for_windows_10_1903_color_banding/ (Fix/Workaround for Windows 10 1903 Color Banding Issues)
This other link below has a slightly different version of the fix from the above two links that might also be worth trying:
* https://www.reddit.com/r/nvidia/comments/c7c578/followup_for_workaround_on_windows_10_1903_color/ (Followup for workaround on Windows 10 1903 Color Banding Issues (Important))
