Hex #66654d or rgb(102,101,77) in RGB space is the tint of yellow. It has hue angle of 57.60 degrees, value = 40 and saturation = 25. #66654d can be obtained by mixing 4 colors: 3 drops of red, 3 drops of blue, 3 drops of green, 1 drop of white.
Nearest safe hex - #666666. Below you can see the block with #66654d color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #66654d to the mixer and play with it.