The phrase "bluish tone" refers to a color that is similar to blue but is not a bright or pure shade of blue. It has a slight tinge or hint of blue. Full definition
It's a very soft, subtle grayish kind of bluish tone that I love. (theinspiredroom.net)
The map shows these areas in light bluish tones where the line shows the 100 and 300 meter water depth. (icyseas.org)
Bathing the painting in bluish tones (an evident nod to Picasso's Blue Period), Brown asserts the history of art to be dynamic, not static. (galleriesnow.net)