Hex #665b00 or rgb(102,91,0) in RGB space is the tint of yellow. It has hue angle of 53.53 degrees, value = 40 and saturation = 100. #665b00 can be obtained by mixing 3 colors: 4 drops of red, 5 drops of green, 1 drop of black.
Nearest safe hex - #666600. Below you can see the block with #665b00 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #665b00 to the mixer and play with it.