唱红脸 comes from Chinese opera, where the red face symbolizes a loyal and upright character. In everyday speech, it means to play the 'good cop' — to act generous, kind, or lenient, often in a calculated way to balance someone playing the 'bad cop' (唱白脸). It is a separable verb (离合词): you can insert a measure word or aspect marker between 唱 and 红脸, as in 唱了一个红脸. The correct pronunciation is chàng hóng liǎn, though the source data lists a different pinyin.