teal background: go into paint and fill with that color(the paint bucket tool most likely) an image with the resolution you want. save with a name that you can remember. (you can probably get away with JPG or PNG, but BMP with something so simple will most likely be the cleanest)
rightclick on your desktop, go to whatever they call customizing your desktop (I don't use windows anymore, or I'd be able to tell you).
find the option for background image or wallpaper or whatever and find the option for custom image/browse for image and pick the file you made earlier and hit enter. hit apply or save changes or whatever it's called nowdays and you're done.
teal background: go into paint and fill with that color(the paint bucket tool most likely) an image with the resolution you want. save with a name that you can remember. (you can probably get away with JPG or PNG, but BMP with something so simple will most likely be the cleanest)
rightclick on your desktop, go to whatever they call customizing your desktop (I don't use windows anymore, or I'd be able to tell you).
find the option for background image or wallpaper or whatever and find the option for custom image/browse for image and pick the file you made earlier and hit enter. hit apply or save changes or whatever it's called nowdays and you're done.