Okay, well can we have some more information. Most likely, this is refering to natural selection. That is, lets say that there are three types of bunnies in the Arctic. One of them is white, one is brown, one is black.
With knowing this, which one do you think will survive and repopulate more than the others.
That would be the white one because it blends into the environment, making it hard for predators to find. There are many factors that can affect this but this is also known as evolution