Hex #66ab99 or rgb(102,171,153) in RGB space is the tint of greenish cian. It has hue angle of 164.35 degrees, value = 67 and saturation = 40. #66ab99 can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of cyan, 3 drops of white, 3 drops of black.
Nearest safe hex - #669999. Below you can see the block with #66ab99 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66ab99 to the mixer and play with it.