go under false colours 假装；冒充

【例句】
He liked to appear religious, but we realized he was sailing under false colours when he refused to give money to the church.
他喜欢让人觉得他很虔诚，但是当他拒绝给教堂捐款时，我们才知道他一直是假装的。

I had so much wisdom as to sail under false colours in this foolish jaunt of mine.
在这次愚蠢的漫游中，我却能机智地更名换姓。