discolouring
v.
使变色，使褪色( discolour的现在分词 );
变化，变色，褪色;
例句:
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Some oil had seeped out, discolouring the grass.
有些油渗出来了，把草地染得变了颜色。
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Work as quickly as possible to prevent the celeriac from discolouring.
来自BBC
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Rub the artichoke halves all over with the lemon juice to prevent them from discolouring.
来自BBC