Hex #669b4d or rgb(102,155,77) in RGB space is the tint of grass green. It has hue angle of 100.77 degrees, value = 61 and saturation = 50. #669b4d can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of green, 3 drops of white, 3 drops of black.
Nearest safe hex - #669966. Below you can see the block with #669b4d color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #669b4d to the mixer and play with it.