Hex #669d8e or rgb(102,157,142) in RGB space is the tint of greenish cian. It has hue angle of 163.64 degrees, value = 62 and saturation = 35. #669d8e can be obtained by mixing 4 colors: 1 drop of red, 5 drops of blue, 4 drops of green, 5 drops of white.
Nearest safe hex - #669999. Below you can see the block with #669d8e color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #669d8e to the mixer and play with it.