Hex #559900 or rgb(85,153,0) in RGB space is the tint of olive. It has hue angle of 86.67 degrees, value = 60 and saturation = 100. #559900 can be obtained by mixing 4 colors: 2 drops of yellow, 1 drop of red, 5 drops of green, 1 drop of black.
Nearest safe hex - #669900. Below you can see the block with #559900 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #559900 to the mixer and play with it.