But those early leaves don't really serve a purpose later on as the plant grows. The purple leaf condition we see happens after the plant is up 18 inches or so and it's usually terminal. After the purple stage, the leaves turn yellow and fall and the plant dries up. The plant does not come back up the following year.
Rick, I get purple cotyledons with seeding quite often if I expose the early seedlings to too much light to quickly. But that never seems to hurt anything--the new first and second leaf continue to grow as if nothing happened. You've most likely seen that, too. But when that happens to fully grown leaves on the entire stem of a nearly fully grown plant, it's a disaster. And it all happens so quickly, usually taking only a couple days.
