Hex #669399 or rgb(102,147,153) in RGB space is the tint of cyan. It has hue angle of 187.06 degrees, value = 60 and saturation = 33. #669399 can be obtained by mixing 4 colors: 2 drops of red, 5 drops of cyan, 4 drops of white, 4 drops of black.
Nearest safe hex - #669999. Below you can see the block with #669399 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #669399 to the mixer and play with it.