How do I Use Shadow Lights w/o Walls Being Shadowed

I've tried a lot of things but the walls are always black.

I have a shadow light pinned to the player, and the walls all have the shadow caster behavior. I want to have the walls be a grey color (at the moment.. later I would like the walls to have textures).

Oh, and is it possible to change the color of the actual shadows?? Because if it is possible, then I would like to have the walls and shadows share a color so that the game can keep it's 'partial 3D' appearance.