The original white lead pigments have oxidized and turned black.

原来白色的铅颜料已经氧化发黑了。

《柯林斯英汉双解大词典》

Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.

绿茶含有30%——40%的可以水萃取的茶多酚，而红茶(绿茶经过发酵后的产物)只含有3%——10%。

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Oolong tea, popular in China, is partly oxidized and is a cross between black and green tea in color and taste.

乌龙茶在中国非常流行，它只进行部分氧化，颜色介于红茶跟绿茶之间。

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