Hex #66af3f or rgb(102,175,63) in RGB space is the tint of grass green. It has hue angle of 99.11 degrees, value = 69 and saturation = 64. #66af3f can be obtained by mixing 4 colors: 5 drops of yellow, 4 drops of blue, 5 drops of green, 1 drop of white.
Nearest safe hex - #669933. Below you can see the block with #66af3f color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66af3f to the mixer and play with it.