A white tee makes your skin look much fairer than a black one.
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culture
Core beauty vocabulary on Xiaohongshu. Chinese beauty culture prizes pale skin (一白遮三丑 'one whiteness hides three ugly features'), so outfit/makeup reviews constantly flag what's 显白 vs 显黑.
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Adjective sense here ('makes skin look fair') is modern, fashion-blog usage. The dictionary entry 'variant of 显摆' (to show off) is an unrelated older sense.