Flowers come in many shapes and colors and contain lots of variety. However, because of natural selection, not all colors will be equally found.
A mutation has caused a red rose to appear, which is very different from the other flowers and not nearly as common.
Flowers reproduce when bees spread around the flower's pollen. What determines which flowers get picked are the color of the petals.
However, the bees are most attracted to the red rose and start to pollinate those instead of the other flowers.
Because the rose's pollen is being spread, the red rose starts to become more common place in a flower field because it's a heritable trait.
Eventually, the red rose will become the most common placed flower color because of the bee's attraction to it. This makes the red petals the desired trait because it means this flower is the most likely to reproduce, thanks to natural selection.