<div class="button">
  <p>マウスオーバーしてね</p>
</div>

<div class="result">
</div>
.button, .result{
  width: 200px;
  height: 100px;
  padding: 20px 0;
  box-sizing: border-box;
  text-align: center;
  color: #fff;
  background: #66b6d5;
  border-radius: 10px;
  margin-bottom: 10px;
}

.button:hover + .result{
  background: #E72458;
}

External CSS

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External JavaScript

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