These are the same model pedals, the purple ones are an older version with a resin (?) shank. But the shape of the pedals is identical.

See the little teeth? The metal shanked ones have only one tooth in the middle, while the purple ones have two teeth. Which way should the foot rest on these? Teeth up, and long side of the pedals towards the front of the bike, or teeth down, and the narrow side of the pedals towards the front of the bike?

And what exactly are the teeth for, anyway?

Inquiring minds want to know