You can set its opacity by default in appearance->theme options->styling options->woocommerce->Product Categories Info Opacity

If you want to make it more customizable, please add this to custom css appearance->theme options->custom code->custom css

.woocommerce .product-category .category-info{background: red; color: #000000}

.woocommerce div.product-category:hover .category-info { background-color: black; color: yellow}