It first appeared when residents of India's Indus Valley discovered that the leaves of indigo plants turned dark blue when dried and, as fermented pulp, clung attractively to garments.

它的第一次出现，是印度河谷的居民发现木蓝属植物的叶子在干枯之后变成深蓝色，且发酵之后的浆状物会牢固地印在衣服上。

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It first appeared when residents of India's Indus Valley discovered that the leaves of indigo plants turned dark blue when dried and, as fermented pulp, clung attractively to garments.

它的第一次出现，是印度河谷的居民发现木蓝属植物的叶子在干枯之后变成深蓝色，且发酵之后的浆状物会牢固地印在衣服上。

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