undertone
/ˈʌndətəʊn/noun
1- a subdued or muted tone of sound or colour低音, 低声; 淡色, 柔和色：
they were talking in undertones.
他们在低声交谈。
1.1
- an underlying quality or feeling内在性质; （感情的）暗流：
the sexual undertones of most advertising.
大多数广告隐含的性内容。