I would like to use the "Mouseover Image for Thumbnails" function (probably with highly compressed WebP images for performance reasons) but would like to have a fallback in form of a simple background color, if no image is set in the post or if WebP isn't supported. This usually works by activating "show Background Color" (and by defining a color) in the Theme customizer. But when I activate it, it won't show the Mouseover Image anymore. It still shows up in the source code though. Is it possible to change the order somehow, like [Thumbnail Image] > over > [Mouseover Image] > over > [Background color]. Or could I somehow define a background color for the Mouseover Image itself via CSS?

Thanks so much and all the best!