<div id="cone"></div>   
#cone {
  width: 300px;
  height: 200px;
background: radial-gradient(gray, transparent),
            conic-gradient(red, yellow, lime, aqua, blue, magenta, red);
border-radius: 50%;
width: 200px; height: 200px;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/prefixfree/1.0.7/prefixfree.min.js
  2. https://leaverou.github.io/conic-gradient/conic-gradient.js