Here's why:
* Calico Pattern: The calico pattern is caused by a random inactivation of one of the X chromosomes in female cats. This means the patches of black, orange, and white fur are present from the start.
* Fur Color: While the overall pattern won't change, the individual color patches might appear slightly different as the cat ages. This could be due to fading of the fur, sun exposure, or even the way the fur lays.
* White Patches: White patches on a calico cat are often due to a different gene, and these can appear larger as the cat ages due to the fur becoming thinner.
In summary, a calico cat's base color pattern is fixed. However, individual patches might appear slightly different as the cat ages due to factors like fur fading or changing hair texture.