Collocations for undertone - noun

dark, sinister
subtle
bitter, sarcastic
racist, sexual
The article was full of racist undertones.

political, religious
There are hints of political undertones throughout the movie.

carry, have
His voice carried bitter undertones.

in an undertone
‘I don't think she's been told yet,’ he said in an undertone.
The couple at the next table were speaking in undertones.