Removing background image - how?

I am feeling quite stupid as I ask a very basic question. I dragged and dropped a background image into all the parts of the website - header, body, footer. It looks awful and I want to remove it. How do I do that? I cannot see anyway to delete just the image and go back to a plain color background. I can delete the whole bric and/or block but that’s not what I want to do. There has to be something quite obvious I am overlooking. Help!

Thanks for helping out the noob.

Right click (r/c) on the image thumbnail in the sidebar, and select ‘clear image’.

Thank you so much.

That was … er… non-obvious but now that I know how it’s done, it works fine.