JSFiddle - React, Tailwind, and code Playground

HTML

<img id="img" src="https://pp.vk.me/c301607/v301607012/3d32/__7RnVwl_ME.jpg" />

CSS

img{
    -webkit-transition: 2s;
    -moz-transition: 2s;
    -ms-transition: 2s;
    -o-transition: 2s;
    transition: 2s;
    -webkit-filter: grayscale(100%);
    filter: grayscale(100%);
}
img:hover{
    -webkit-transition: 2s;
    -moz-transition: 2s;
    -ms-transition: 2s;
    -o-transition: 2s;
    transition: 2s;
    -webkit-filter: grayscale(0%);
    filter: grayscale(0%);
}