JSFiddle - React, Tailwind, and code Playground

HTML

<div class="border red-mark"></div>

CSS

div {
    width: 200px;
    height: 200px;
    position: relative;
}

.border {
    border: 15px silver solid;
}

.red-mark:before {
    content: '';
    display:block;
    width: 15px;
    position: absolute;
    top: -15px;
    left: -15px;
    bottom: -15px;
    background: red;
}