Hex #558f39 or rgb(85,143,57) in RGB space is the tint of grass green. It has hue angle of 100.47 degrees, value = 56 and saturation = 60. #558f39 can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of green, 2 drops of white, 3 drops of black.
Nearest safe hex - #669933. Below you can see the block with #558f39 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558f39 to the mixer and play with it.