Defualt Grey Background on Video Thumbnail

hey guys,

I am wondering how to change the background colour of my video thumbnails on the product page and product grid?

It defaults to a grey colour but I just want white which is what the video actually has.

I have seen a proposed solution to replace the thumbnail with a still im age with a white background but that will be quite time consuming to change every product.

There must be a setting somewhere that is pulling that colour code and applying it? If I could just change it to white that would be great.

See the thumbnails below the video on this link https://www.glowdiamonds.com.au/products/thee-stone-pear-cut-diamond-ring