Hex #558e8e or rgb(85,142,142) in RGB space is the tint of cyan. It has hue angle of 180.00 degrees, value = 56 and saturation = 40. #558e8e can be obtained by mixing 4 colors: 1 drop of yellow, 1 drop of red, 2 drops of blue, 2 drops of cyan.
Nearest safe hex - #669999. Below you can see the block with #558e8e color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558e8e to the mixer and play with it.