Have you ever stuck your nose into a flower to sniff its perfume? I've done that and I got the yellow powder on my nose. That made me a little bit like a bee.
This is a tray of pollen that a beekeeper has collected. You can see that it's mostly a green colour. The beekeeper will put this pollen in a jar to sell to people. (In another story I'll tell you how the beekeeper collects pollen from the bees).