Hex #998900 or rgb(153,137,0) in RGB space is the tint of yellow. It has hue angle of 53.73 degrees, value = 60 and saturation = 100. #998900 can be obtained by mixing 4 colors: 5 drops of yellow, 1 drop of red, 1 drop of green, 3 drops of black.
Nearest safe hex - #999900. Below you can see the block with #998900 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #998900 to the mixer and play with it.