Memory foam mattress topper?

I just got the memory foam mattress topper, but I don't know which side goes up first? It's not on the directions. The green side is firmer, but if you press down with your hand, it holds the handprint. The white side is squishier, but when you press down, it doesn't hold your hand print, like it doesn't keep it's shape. Which side do you think I should sleep on?