Hex #666839 or rgb(102,104,57) in RGB space is the tint of yellow. It has hue angle of 62.55 degrees, value = 41 and saturation = 45. #666839 can be obtained by mixing 4 colors: 2 drops of yellow, 4 drops of red, 5 drops of blue, 4 drops of green.
Nearest safe hex - #666633. Below you can see the block with #666839 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #666839 to the mixer and play with it.