Hex #669d99 or rgb(102,157,153) in RGB space is the tint of cyan. It has hue angle of 175.64 degrees, value = 62 and saturation = 35. #669d99 can be obtained by mixing 4 colors: 1 drop of magenta, 5 drops of blue, 4 drops of green, 5 drops of white.
Nearest safe hex - #669999. Below you can see the block with #669d99 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #669d99 to the mixer and play with it.