* Pigmentation: Cat fur color is determined by the presence or absence of different pigments, primarily melanin. Melanin comes in two forms: eumelanin (which creates black and brown colors) and phaeomelanin (which creates reddish and yellowish colors).
* Blue is a structural color: Blue in animals, like the blue feathers of a blue jay, is not due to pigment but rather the scattering of light by microscopic structures. Cats don't have the necessary structures in their fur to create this effect.
* Dilute genes: While there are cats with "blue" eyes, these are actually a dilute form of brown or green eyes, meaning they have less melanin present. This is different from true blue fur.
So, while we can appreciate cats with blue eyes, a truly blue cat remains a fictional creature!