Hex #558140 or rgb(85,129,64) in RGB space is the tint of grass green. It has hue angle of 100.62 degrees, value = 51 and saturation = 50. #558140 can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of green, 3 drops of white, 5 drops of black.
Nearest safe hex - #669933. Below you can see the block with #558140 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558140 to the mixer and play with it.