Change a form theme
You created questions for your form, and now you’re thinking about form design: the background design and colors. You want the form to have a bit more visual pop. How do you get that? Use themes!
1. In Microsoft Forms, open the form for which you
want to change the theme.
2. Click Theme at the top right of the design window
and pick the colour or background you want.
3. If you prefer another background image, such as
one stored on your computer, click the Upload image icon 
, and then select one of the following:
o Image Search - Enter your search text in the Bing
search box, and then click the Search button to see your search results. Pick the background image you want, and then click Add.
o OneDrive - Click the OneDrive folder that contains
your image. Select the image, and then click Add.
o Upload - Navigate to the folder that contains your
image. Select the image you want, and then click Open.
If you want to replace the image you selected with a
different one, click the trash can icon on the current image, and then click the Upload image icon 
to start the process over.