Is the surface of TrES-2b actually dark?
I don't know, how it works there, but perhaps it is easier to imagine, how it could look. 

TrES-2b is a gas giant, so it doesn't have a well defined surface. When you are somewhere in the atmosphere then:

-When looking up, you will see the light, as deep sea creatures do. The amount of light and its color will depend on how deep you are.

-When looking down, it should be dark (black), comparing to how it looks up. Otherwise, the atmosphere would be reflecting light.

-When looking to the sides, it should also be dark, for if the light were scattered at some angles, it would also be scattered upwards.

So, one simplest possible model is: like in deep sea.

Note, that at some other wavelengths, particularly in infrared, it all can look very differently.