<p class="box">
    Lorem ipsum dolor sit amet consectetur adipisicing elit. Voluptates neque iure atque perferendis harum, excepturi, amet laboriosam nam quidem et eligendi reprehenderit similique eius maiores animi voluptatem error ab in.
</p>
html {
  --color: blue;
}

.box {
  color: var(--color);
}

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