Hex #557f80 or rgb(85,127,128) in RGB space is the tint of cyan. It has hue angle of 181.40 degrees, value = 50 and saturation = 34. #557f80 can be obtained by mixing 4 colors: 1 drop of magenta, 2 drops of blue, 2 drops of green, 1 drop of white.
Nearest safe hex - #666699. Below you can see the block with #557f80 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #557f80 to the mixer and play with it.