Hex #153639 or rgb(21,54,57) in RGB space is the tint of cyan. It has hue angle of 185.00 degrees, value = 22 and saturation = 63. #153639 can be obtained by mixing 4 colors: 1 drop of red, 4 drops of blue, 2 drops of green, 5 drops of black.
Nearest safe hex - #003333. Below you can see the block with #153639 color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #153639 to the mixer and play with it.