If the characters have the ability to see in the dark, even if it's black and white, can they tell where shadows are cast?

This seems particularly to be in question when something like Warlock's Devil's Sight, which allows to see in complete darkness with no problems.

::Edit::  
Think about someone in the Underdark, it's pitch black except where shadows hit a pillar, however someone with Devil's Sight would be able to see normally, how would they discern where the shadows were being cast if you can see in pitch darkness?

The question kind of boils down to a biological one, most creatures that can see in the dark don't see well in the light, this is a "magical" ability for the most part, but it seems like if you don't need light to see normally, you may not be able to discern light vs darkness at all.

>**Pg. 119 PHB**  
>Devil's Sight  
>You can see normally in darkness, both magical and nonmagical to a distance of 120 feet.

So to rephrase the question:  
If light is unnecessary to see everything normally (to a certain range) would you be able to detect the absence of light?  In other words, if you see normally, full color, everything is like it's got perfect lighting within 120 ft, would you actually be able to discern the difference between light and darkness?