Hex #558b87 or rgb(85,139,135) in RGB space is the tint of cyan. It has hue angle of 175.56 degrees, value = 55 and saturation = 39. #558b87 can be obtained by mixing 4 colors: 1 drop of red, 5 drops of blue, 3 drops of green, 3 drops of white.
Nearest safe hex - #669999. Below you can see the block with #558b87 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558b87 to the mixer and play with it.