no change the background color

To add a background color box add a class name to the Badge Class
For mine I used free-shipping-bubble in the Badge Class

I added the following css to my theme css file
This creates a yellow box background with white text that is positioned at the top right of the product image

.free-shipping-bubble {
background-color: #FFBA00;
border: 1px solid #FF8400;
padding: 5px;
color: #FFFFFF !important;
position: absolute;
top: 0px;
right: 0px;
}