The lights and shadows look alright. Would it be too much work to add shaded tiles, so that there can be cast shadows? The right-facing sides are so dark compared to the other surfaces that it looks like there should be a strong directional light, which means cast shadows.
I don't like the shadows underneath the robots, they don't fit the isometry and their softness looks out of place with how sharp everything else is.
What are the little triangular bits on the bottom? They look alright on the dark side, but look detached on the light side. Perhaps get rid of the bright highlight? It looks a bit out of place and it gives the triangles more contrast than they warrant.
The colours are fine, though I can't say that looking at a screen full of grey is particularly fun. The greys in this palette are nice, but I think they're best used sparingly. This is more of a design consideration than a colour one though - try to theme the levels to require fewer flat, boring grey surfaces. You can convey "industrial, metal-filled" without making everything grey. Think about the light sources, and other textures that would be found in this sort of setting. Give it some mood.
