Pink mint (original color) next to sun-faded mint
Here's a picture of the underside of the mint. Again, you can see the contrast between the faded edges, which perhaps got some sunlight because the mint isn't actually quite flat, and so a little sun would have shone on the very edges, and also perhaps because the mint was sitting on a reflective pie tin. Whatever the reason, the difference is significant.
I hope my dermatologist sister is proud of me writing about the strong effects of sunlight! I wonder if the mint would have been protected against fading by a coating of sunscreen?