<!DOCTYPE html>
<style>
  .box {
    display: inline-block;
    height: 100px;
    width: 200px;
    border: 1px solid black;
  }

  .linear1 {
    background-image: linear-gradient(to right, red -80%, -80%, green);
  }

  .linear2 {
    background-image: linear-gradient(to right, red, 0%, green);
  }

  .linear3 {
    background-image: linear-gradient(to right, green, 100%, red);
  }

  .linear4 {
    background-image: linear-gradient(to right, green, 50%, blue);
  }

  .linear5 {
    background-image: linear-gradient(to right, red, 25%, green, 75%, blue);
  }

  .linear6 {
    background-image: linear-gradient(to right, green, 50%, red, 50%, blue);
  }

  .radial1 {
    background-image: radial-gradient(ellipse, red -80%, -80%, green);
  }

  .radial2 {
    background-image: radial-gradient(ellipse, red, 0%, green);
  }

  .radial3 {
    background-image: radial-gradient(ellipse, green, 100%, red);
  }

  .radial4 {
    background-image: radial-gradient(ellipse, green, 50%, blue);
  }

  .radial5 {
    background-image: radial-gradient(ellipse, red, 25%, green, 75%, blue);
  }

  .radial6 {
    background-image: radial-gradient(ellipse, green, 50%, red, 50%, blue);
  }
</style>

<div class="linear1 box"></div>
<div class="linear2 box"></div>
<div class="linear3 box"></div>
<div class="linear4 box"></div>
<div class="linear5 box"></div>
<div class="linear6 box"></div>
<div class="radial1 box"></div>
<div class="radial2 box"></div>
<div class="radial3 box"></div>
<div class="radial4 box"></div>
<div class="radial5 box"></div>
<div class="radial6 box"></div>