Well, I am completely new to CC3 (picked it up last month and yet to have the tinme to play properly), but I would suggest creating a stair symbol as suggested above, with a generic drop shadow with it. Once you have that place the stairs as required. After you have have those stairs placed, put a gradient from top of stairs to bottom of light (very) to dark grey. How dark you want the bottom to be would depend on how deep you are going, and vary the opacity to what suits your needs. I know placing all of your stairs first is a small hassle, but it will avoid having stairs that alternate from light to dark and back to light again...as apears in your example...

Remember, I don't know CC3 much so please ignore the above if this is not possible in that prog....