Gray background in Slideshow

Hi, to make the background white, add this to your Customize > Additional CSS:

.wp-block-jetpack-slideshow .wp-block-jetpack-slideshow_slide {
    background: white !important;
}

I usually prefer not to use !important but, that case warrants it ??

As for the optimal size: I’d recommend about twice as wide as the media width for your theme. Usually you can find that number in the CSS page, too. For the height, it doesn’t matter, but I’d recommend using the same height and width ratio for all of the image so the slideshow doesn’t seem to shrink and grow.

Hoping this helps!

You are a genius!
Both the solutions offered worked perfectly!????

One question though, what does “!important” do to the page?

CSS code adheres to a priority according to which the code is run and applied to your site. This allows you to add global styles for your site, but then add additional rules for specific elements. Whatever appears last in the stylesheets for any particular element, is what determines how it looks on your site.

Adding !important to a CSS declaration means it will disregard that priority and force that particular styling to always apply, even if declarations appearing later in the stylesheet overrides it.

In general, this is not a good idea, as it “breaks” the way CSS is designed to work – it can make it impossible to override a particular style with later CSS. But in this case it’s not likely to cause that problem, as the code is very specific to the slideshow gallery, and shouldn’t affect anything else on your site.