JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div {
  font-size: 1em;

  position: relative;

  width: 30px;
  height: 30px;
  margin: 0 auto;

  border-radius: 50%;
  background: linear-gradient(to right, blue 50%, green 70%, red 100%);
  /* background: url('http://s1.iconbird.com/ico/0912/MedICOFreeMedicalIcons/w64h641347633749nuclear.png') no-repeat center; */
  box-shadow: 0 0 0 .3em white, 0 0 0 .35em red;
}