小编Fla*_*uso的帖子

.back{
  background-color: grey;
  width: 100%;
  height: 200px;
  display: inline-grid;
  align-items: center;
  overflow: hidden;
}

.line{
  height: 3px;
  background: linear-gradient(to right, yellow, purple, blue, green, red, orange);
  transform: rotate(-10deg);
}

<div class="back">
  <div class="line"></div>
</div>