Hex #558a87 or rgb(85,138,135) in RGB space is the tint of cyan. It has hue angle of 176.60 degrees, value = 54 and saturation = 38. #558a87 can be obtained by mixing 4 colors: 2 drops of yellow, 2 drops of magenta, 5 drops of cyan, 3 drops of black.
Nearest safe hex - #669999. Below you can see the block with #558a87 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558a87 to the mixer and play with it.