Hex #666000 or rgb(102,96,0) in RGB space is the tint of yellow. It has hue angle of 56.47 degrees, value = 40 and saturation = 100. #666000 can be obtained by mixing 4 colors: 1 drop of yellow, 3 drops of red, 4 drops of green, 2 drops of black.
Nearest safe hex - #666600. Below you can see the block with #666000 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #666000 to the mixer and play with it.