Hi Marcus,

Currently you can't give a specific colour to your objects in MoI. It will probably be for V.2 (I hope so). There are no texturing options as well.
The best solution is to add colour to your mesh objects in another application. You can also create or edit UV maps in other applications for texturing (If you don't have a commercial software which can do that, you can use free software like Blender or Wings 3D...)

HTH

I would think that Photoshop would have some way to adjust the color built in there as well... But I haven't messed around with the new 3D features in Photoshop yet so I'm just not familiar with them.

- Michael