Ok, just to verify, when you say "double sided", do you mean doing something like using the shell tool to give it depth, or are you applying a double-sided material to it instead?
If you're modifying the geometry to make it double-sided and it changes color or loses its texture, then more than likely the UVs got reset or the material got unassigned. Reapply the material to the shield and then use the UV tool to remap the material w/ texture on both sides of the shield.
If you're using a double-sided material on an open mesh (is only a polygon thick, like paper), you have to click on the "back" button in the material editor and reapply the textures and colors to the back side to mirror the front side. Make sure all of the parameters are the same.
If that's not what you meant, please clarify a little more on how you've got it set up and maybe a screenshot of the problem in effect.