Something else with keeping that same senerio in mind...
When new batches of fish come into a store, their colors are washed out, especially in the bags and can be very difficult to positively ID them (if there are several tetras in the order) from each other. Accidently mixing batches of fish is common...LOL. I've done it myself as well as many other employees. They usually get their colors back while floating in the tanks acclimating to temps, but sometimes not until they've been released and adjusted to some degree. Then we can see which tetras are which. Green tetras aren't much different from neons and brandy new, they can appear identical. Don't worry. They're not prejudice. They will typically school with each other.