By default, Windows 10 will display your desktop wallpaper as the logon screen background. If you wish to display a solid color as a background for your Windows 10 logon screen, then you will be required to edit the Registry. A Windows 10 user can replace the desktop background via Personalization settings. This will change the logon screen too. But if you wish to remove the logon screen background and set a solid color, read on.
Set solid color as Windows 10 logon screen background
Please note, that this involves editing the Windows Registry. Wrongly editing the Registry can cause your computer to stop functioning. If you are uncertain or not completely comfortable editing the Registry, we recommend sticking with the default Windows 10 log-in screen. If not, create a system restore point and move on.
Type regedit in taskbar search and click on the result to open the Registry Editor.
Navigate to the following registry key:
Now in the right side, right-click in the empty space and from the context menu, chose New > DWORD (32-Bit), name it DisableLogonBackgroundImage and give it a value 1.
This will remove the default logon screen image and force Windows 10 to take a solid color the accent color from your desktop wallpaper.
If you wish to select your own color, open Settings > Personalization > Colors and turn the slider to the Off position for Automatically pick an accent color from my desktop.
Restart your computer and check.
To reverse the changes, you need to simply delete the created DWORD or change its value to 0.
Trust this works for you! It worked for me on my Windows 10 Pro 64-bit PC.