Once there was a species of mice in a forested area that had a variation of color, most were different shades of brown and a small handful was a pure white color.
There was not many pure white mouse because they were easier for their predators (tigers) to see in the brown and green color scheme. Whilst brown mouse could camouflage themselves in to the trees.
But, on one day when it all of the sudden got really cold, would increase the white mice population. All of the sudden, aleast a million snowflakes started to fall and the water started to freeze over.
The mice awoke after the brutal storm and realized the world around them was pure white. It was a sight for sore eyes, nothing they have seen before.
The mice went about their day but, when they came across a tiger, it never even realized the white mouse was there. The only prey it saw was the brown mouse because its dark color stood out in the pure white snow. While, the pure white mouse blended in perfectly.
Due to white mice being able to camouflage with the snow and brown mice not being able to, more white mice survived than brown mice. Resulting in more offspring skyrocketing the population of white mice.