There is no simple formula for #c5cbcb, but we have one for color #b3bbbb, that is similar to #c5cbcb by 97.7%.
Color #b3bbbb name: grayish cyan
Hex #b3bbbb or rgb(179,187,187) in RGB space is the tint of cyan. It has hue angle of 180.00 degrees, value = 73 and saturation = 4. #b3bbbb can be obtained by mixing 4 colors: 2 drops of magenta, 1 drop of cyan, 2 drops of green, 5 drops of white.
Nearest safe hex - #cccccc. Below you can see the block with #b3bbbb color and its structure: in procentage ratio and in drops of pigments. Click "TRY" button to move #b3bbbb to the mixer and play with it.