Why does an animal live in a habitat that has the same color or shape as its body?

So it can have a chance of survival and reproduce, this is called Survival of the Fittest. Fittest as in most adapted.

Animals mix into their surroundings by being the same color or shape as their habitat because this allows them to survive. If they can't be spotted, they won't be eaten. This cycle goes on to the point where all the animals that don't mix to their habitat die off, and the ones that do mix, keep reproducing.