Add hover price and box to products

[alyssasps]

I successfully did the add price on hover shown here: Solved: Showing price and name when hover (DAWN) - Shopify Community - but I now want to add a box (like a text box for the price) because as it is currently the text is black with no overlay over the image it makes it very hard to see the price, and is not accessibly. I'd like to know what css code to add, probably in theme.liquid or base.css?? Either a text box where I can specify the hex code for both the box and the text color, or add a solid color overlay so that the price is more visible.

Thanks in advance!