Hex #66cf33 or rgb(102,207,51) in RGB space is the tint of grass green. It has hue angle of 100.38 degrees, value = 81 and saturation = 75. #66cf33 can be obtained by mixing 3 colors: 1 drop of yellow, 3 drops of green, 1 drop of white.
Nearest safe hex - #66cc33. Below you can see the block with #66cf33 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66cf33 to the mixer and play with it.