Hex #558539 or rgb(85,133,57) in RGB space is the tint of grass green. It has hue angle of 97.89 degrees, value = 52 and saturation = 57. #558539 can be obtained by mixing 3 colors: 3 drops of red, 2 drops of cyan, 4 drops of green.
Nearest safe hex - #669933. Below you can see the block with #558539 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558539 to the mixer and play with it.