Gov issued photo id with citizenship verification should absolutely be required for voting in a federal election.
Also don't make them identical except for very fine printing that differentiates citizens from non-citizens (I'm looking at you, CA).
Especially now that we're going to Real ID, and it appears many states are still going to offer driver's licenses to citizens in both Real ID and standard form. As I mentioned in another topic, starting in JAN, the CA non-real ID license will look identical - exactly identical - for citizens and non-citizens.
Then the only difference between the Real ID license and non-Real ID will be a small marker in the upper right for Real ID, and "Federal Limits Apply" (in fine print) for non-Real ID. Again, either a citizen or non-citizen can carry a "Federal Limits Apply" license, and there is no way to distinguish citizenship. IMO, they should be completely different colors or something else visibly and immediately distinguishable.