Last few days I noticed that after I turn the PC on, when the Lock Screen shows up its black and white (greyscale). I don't know why its this way, or is this a new feature? I did not install a feature update, although smaller updates are set to auto install. This problem does not happen after I sign into the desktop (the desktop is in full color), and if I sign out from the desktop, then the lock screen is also in full color. I searched the internet but couldn't find a solution. This never happened before.
This is my Windows build: Windows 10 Pro, 1903, 18362.356
EDIT: Nevermind. I found out the problem. Windows Spotlight just served me a photo of a picturesque mountain for my lock screen, only that its in black and white. As all other texts (like time, date, weather, default avatar) are also in white, I was fooled into thinking that the display itself has lost its color. Also for some reason, this photo of a mountain stayed around for about a week and didn't change. My bad.
Best Answer
I had this issue the real black and white issue and it wasn't high contrast mode hot key left alt left shift printscreen button and confirmation to get high contrast mode with color like yellow.
See video https://tiny.cc/oibwmon
The solution for me was in AMD Catalyst none of the options in tabs worked but I recently found a preferences button top left and reset to factory default and color is restored.
Somehow AMD can greyscale certain outputs?
Original Answer:i solved color problem in amd catalyst software for my graphics card there is a hidden button top right called preferences by restoring to factory default i remedied the problem