JSFiddle - React, Tailwind, and code Playground

HTML

<div class="two-colour-background">
    This is a div with multiple background colours.
</div>

CSS

.two-colour-background {
    width: 100px;
    height: 100px;
    background: -webkit-linear-gradient(left, grey, grey 30%, white 30%, white);
    border: solid 10px #000;
}