Hex #559940 or rgb(85,153,64) in RGB space is the tint of grass green. It has hue angle of 105.84 degrees, value = 60 and saturation = 58. #559940 can be obtained by mixing 4 colors: 4 drops of yellow, 3 drops of cyan, 1 drop of green, 4 drops of black.
Nearest safe hex - #669933. Below you can see the block with #559940 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #559940 to the mixer and play with it.