JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outer1"><!--
    --><div class="inner top left">&nbsp;</div><!--
    --><div class="inner top right">&nbsp;</div><!--
    --><div class="inner bottom left">&nbsp;</div><!--
    --><div class="inner bottom right">&nbsp;</div><!--
--></div>
<br>
<div id="outer2"><!--
    --><div class="inner top left"></div><!--
    --><div class="inner top right"></div><!--
    --><div class="inner bottom left"></div><!--
    --><div class="inner bottom right"></div><!--
--></div>

CSS

* {
    box-sizing: border-box;
    margin:0;
    padding:0;
}
body {
    background-color: black;
}
#outer1, #outer2 {
    width:200px;
    height:200px;
    margin:auto;
    border-radius:50%;
    line-height:0px;   /*<------------*/
}
.inner {
    height: 50%;
    width:50%;
    display: inline-block;
}
.top.left {
    background-color: green;
    border-radius: 100% 0 0 0;
}
.top.right {
    background-color: #ff3300;
    border-radius: 0 100% 0 0;
}
.bottom.left {
    background-color: darkcyan;
    border-radius: 0 0 0 100%;
}
.bottom.right {
    background-color: darkred;
    border-radius: 0 0 100% 0;
}