<body>
  <div class="container"></div>
</body>
:root {
	--bg-color: #d7d7d7;
}

@media (max-width: 999px) {
	:root {
		--bg-color: #bca9a9;
	}
}

@media (max-width: 599px) {
	:root {
		--bg-color: #a47777;
	}
}

.container {
	background-color: var(--bg-color);
	height: 50vh;
}

External CSS

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External JavaScript

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