Hex #555d68 or rgb(85,93,104) in RGB space is the tint of blue. It has hue angle of 214.74 degrees, value = 41 and saturation = 18. #555d68 can be obtained by mixing 3 colors: 1 drop of blue, 3 drops of white, 5 drops of black.
Nearest safe hex - #666666. Below you can see the block with #555d68 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #555d68 to the mixer and play with it.