JSFiddle - React, Tailwind, and code Playground

HTML

<div class="addFav">
Using RGB for a fallback is nice. It's no-brainer work because all you have to do is duplicated the RGBa value, remove the "a" and remove the 4th (opacity)
</div>

CSS

.addFav {
    background:rgba(146,146,146,0.1);
    border:1px solid red;
    height:200px;
    width:200px;
    color:#333;
    padding:15px;
}