JSFiddle - React, Tailwind, and code Playground

HTML

<h3><span class="red">1</span>A grey circle with number inside</h3>

CSS

span.red {
  background: red;
   border-radius: 0.8em;
  -moz-border-radius: 0.8em;
  -webkit-border-radius: 0.8em;
  color: #ffffff;
  display: inline-block;
  font-weight: bold;
  line-height: 1.6em;
  margin-right: 15px;
  text-align: center;
  width: 1.6em; 
}

span.grey {
  background: #cccccc;
  border-radius: 0.8em;
  -moz-border-radius: 0.8em;
  -webkit-border-radius: 0.8em;
  color: #fff;
  display: inline-block;
  font-weight: bold;
  line-height: 1.6em;
  margin-right: 15px;
  text-align: center;
  width: 1.6em; 
}

span.green {
  background: #5EA226;
  border-radius: 0.8em;
  -moz-border-radius: 0.8em;
  -webkit-border-radius: 0.8em;
  color: #ffffff;
  display: inline-block;
  font-weight: bold;
  line-height: 1.6em;
  margin-right: 15px;
  text-align: center;
  width: 1.6em; 
}

span.blue {
  background: #5178D0;
  border-radius: 0.8em;
  -moz-border-radius: 0.8em;
  -webkit-border-radius: 0.8em;
  color: #ffffff;
  display: inline-block;
  font-weight: bold;
  line-height: 1.6em;
  margin-right: 15px;
  text-align: center;
  width: 1.6em; 
}

span.pink {
  background: #EF0BD8;
  border-radius: 0.8em;
  -moz-border-radius: 0.8em;
  -webkit-border-radius: 0.8em;
  color: #ffffff;
  display: inline-block;
  font-weight: bold;
  line-height: 1.6em;
  margin-right: 15px;
  text-align: center;
  width: 1.6em; 
}