Unfortunately I think you'll find that your example won't change any minds because:
1. Creationists won't accept this as an example of evolution. What they're looking to "disprove" is the idea that man evolved from apes, or rather that given time, one kind of animal species will transform into a completely new and distinct species. But in your example the moths are still moths, just in a different color.
2. More seriously you can't fight illogic with logic.