Hex #556979 or rgb(85,105,121) in RGB space is the tint of blue. It has hue angle of 206.67 degrees, value = 47 and saturation = 30. #556979 can be obtained by mixing 4 colors: 3 drops of magenta, 4 drops of blue, 4 drops of green, 1 drop of white.
Nearest safe hex - #666666. Below you can see the block with #556979 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #556979 to the mixer and play with it.