Hex #556780 or rgb(85,103,128) in RGB space is the tint of blue. It has hue angle of 214.88 degrees, value = 50 and saturation = 34. #556780 can be obtained by mixing 3 colors: 3 drops of blue, 4 drops of white, 5 drops of black.
Nearest safe hex - #666699. Below you can see the block with #556780 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #556780 to the mixer and play with it.