Hello Rose,
If you meant that you want a solid color for the background, then while
changing your background wallpaper, be sure to select
Solid Colors from the
Picture Location drop down menu like below. You will then be able to select a color to be a blank wallpaper.
In additition, you could check the
Remove background images (where available) box in the Ease of Access Center using the tutorial below to force nothing but a solid color background to be available.
Remove Background Images (where available)
Hope this helps,
Shawn