<div class="box1"></div>
<div class="box2"></div>
.box1{
  height:100px;
  outline:1px solid;
  background-image: linear-gradient(90deg,red 0%,orange 20%,yellow 40%,green 60%,blue 80%,violet 100%);
}

.box2{
  height:100px;
  outline:1px solid;
  background-image: linear-gradient(90deg,red 0%,orange 20%,yellow 40%,green 60%,blue 10%,violet 100%);
}

External CSS

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External JavaScript

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