Hex #556b72 or rgb(85,107,114) in RGB space is the tint of bluish cian. It has hue angle of 194.48 degrees, value = 45 and saturation = 25. #556b72 can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of blue, 2 drops of white, 3 drops of black.
Nearest safe hex - #666666. Below you can see the block with #556b72 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #556b72 to the mixer and play with it.