Hex #55819d or rgb(85,129,157) in RGB space is the tint of blue. It has hue angle of 203.33 degrees, value = 62 and saturation = 46. #55819d can be obtained by mixing 3 colors: 1 drop of yellow, 4 drops of blue, 1 drop of white.
Nearest safe hex - #669999. Below you can see the block with #55819d color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #55819d to the mixer and play with it.