Hex #558b40 or rgb(85,139,64) in RGB space is the tint of grass green. It has hue angle of 103.20 degrees, value = 55 and saturation = 54. #558b40 can be obtained by mixing 4 colors: 1 drop of red, 5 drops of green, 3 drops of white, 3 drops of black.
Nearest safe hex - #669933. Below you can see the block with #558b40 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #558b40 to the mixer and play with it.