What's the difference between red&yellow watermelon?

Lycopene is the only difference. It's an antioxidant; red watermelons have it, yellow ones don't. It's the same antioxidant that makes tomatoes red. Flavor wise, they are about the same; only sometimes are yellow watermelons sweeter ("honey-like").

They are beautiful to look at and seem to have a honey like flavor. I like serving both for large gatherings because of the visual.