JSFiddle - React, Tailwind, and code Playground

HTML

<div id="FadeIn3"></div>

CSS

#FadeIn3 {
    animation-delay: 3s;
    -webkit-animation-delay: 3s;
    animation: FadeIn 3s;
    -webkit-animation: FadeIn 3s;
    height: 20px;
    width: 20px;
    background: #f00;
}
@keyframes FadeIn {
    0% {
        background: #0f0;
    }
    100% {
        background: #00f;
    }
}