Hex #558a8e or rgb(85,138,142) in RGB space is the tint of cyan. It has hue angle of 184.21 degrees, value = 56 and saturation = 40. #558a8e can be obtained by mixing 3 colors: 2 drops of cyan, 3 drops of white, 4 drops of black.
Nearest safe hex - #669999. Below you can see the block with #558a8e color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558a8e to the mixer and play with it.