Have you understood the undertone of his words?

你明白他话的弦外之音了吗？

People with cool skin tones (blue undertones in the skin) are well suited to light clothing.

冷色调皮肤（皮肤底色为蓝色）的人非常适合穿浅色衣服。

Please speak up, because I can't hear your undertone.

请大声一点，因为我听不清你的低音。