What are Blue Cats?

Caitlin Dempsey


A gray cat with copper eyes and short limbs standing looking back on grass.

Despite the name, blue cats aren’t actually blue. ‘Blue’ fur in the cat fancier world is actually a shade of gray that has blue undertones.

Genetics behind the ‘blue’ fur color in cats

The genetic underpinning of this color lies mainly in a specific gene known as the “dilution gene.” Cats have black or brown fur as a result of a pigment called eumelanin. The dilution gene acts as a modifier of this pigment, spreading it out in such a way that it appears diluted or ‘watered-down,’ leading to the blue-grey appearance. To display this hue, a cat needs to inherit two copies of the recessive allele (dd) for the dilution of the pigment to manifest, leading to a blue-grey coat instead of a black fur coat.

Cat breeds that are blue

Several breeds are renowned for their blue color.

Russian blue

The most renowned blue cat breed is the Russian Blue. The Russian Blue is a cat breed distinguished by a short, plush coat of bluish-gray fur, striking green eyes, and a generally reserved but affectionate nature.

A Russian blue cat with gray fur and yellow eyes lying on a light greenish carpet.
The Russian blue cat is the most well-known “blue” cat breed. Photo: © Rob Rye/stock.adobe.com.

British blue

The British Blue, more commonly referred to as the British Shorthair in the blue variant, is a breed of domestic cat originating from the United Kingdom. British blues are characterized by dense, plush, and bluish-gray coat, rounded face, and dense muscular structure. The eyes of a typical British Blue are copper or gold, creating a striking contrast with the cat’s coat color.

While the British Shorthair cat can come in a variety of colors and patterns, the blue variant is particularly popular and often what people first think of when the breed is mentioned.

A British Shorthair cat with blue (gray) fur lying on very green grass.
The British Blue is a color type of the British Shorthair cat. Photo: © Phil/stock.adobe.com.

Korat blue cat

The Korat is a domestic cat that originates from Thailand. Korat cats are known for their heart-shaped faces and green eyes.

A charcoal gray cat with green eyes sitting on a white chair.
A Korat cat with blue coloring. Photo: © tammarat/stock.adobe.com.

Chartreux blue

The Chartreux cat is a breed that originates from France. These cats are large and muscular with relatively short limbs. The Chartreux cat has eyes which can range from copper to gold with deep orange being the prized eye color. The fur color of the Chartreux is always blue-gray but can vary from ash to slate.

A gray cat with copper eyes and short limbs standing looking back on grass.
The Chartreux cat is know for having a blue coat and relatively short limbs. Photo: © Christophe Fouquin/stock.adobe.com.

Mixed breed blue cats

Blue coloring in cats is not exclusive to any particular breed and can occur naturally in random-bred populations. The ‘blue’ fur coat color can also show up in mixed breed cats as long as they receive recessive dilute genes from each parent that fades out the black coloring of their fur.

If both parent cats carry at least one copy of the recessive dilution allele (dd), they can produce offspring with a blue coat. Even if neither parent exhibits a blue coat themselves, they may be carriers of the dilution gene. 

A charcoal gray cat with yellow eyes sitting the arm of a tree.
A mixed breed cat with a blue fur coat. Photo: Caitlin Dempsey.

Blue tabby cats

In tabby cats, the blue coloring appears as gray stripes against a lighter gray base color.

A gray tabby sitting on a black leather couch.
A blue tabby. Photo: Caitlin Dempsey.

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About the author
Caitlin Dempsey
Caitlin Dempsey holds both a master's in Geography from UCLA and a Master of Library and Information Science. She is the editor of Geographyrealm.com and an avid researcher of geography and feline topics. A lifelong cat owner, Caitlin currently has three rescued cats: an orange tabby, a gray tabby, and a black cat.