Hex #66a899 or rgb(102,168,153) in RGB space is the tint of greenish cian. It has hue angle of 166.36 degrees, value = 66 and saturation = 39. #66a899 can be obtained by mixing 4 colors: 2 drops of cyan, 1 drop of green, 4 drops of white, 3 drops of black.
Nearest safe hex - #669999. Below you can see the block with #66a899 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66a899 to the mixer and play with it.