Hex #558e9f or rgb(85,142,159) in RGB space is the tint of bluish cian. It has hue angle of 193.78 degrees, value = 62 and saturation = 47. #558e9f can be obtained by mixing 4 colors: 2 drops of blue, 3 drops of cyan, 5 drops of white, 5 drops of black.
Nearest safe hex - #669999. Below you can see the block with #558e9f color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558e9f to the mixer and play with it.