A solid grey cat has a quiet, velvety look, like a shadow that decided to sit down. Cat breeders don’t call it grey, though. They call it blue. And the colour isn’t a colour of its own at all. It’s black, watered down.
In short
| What makes grey? | The dilute gene, acting on black. |
|---|---|
| How? | The pigment clumps instead of spreading evenly. |
| What else does it do? | Ginger turns cream. Chocolate turns lilac. |
| Inherited how? | A kitten needs a copy from both parents. |
| On the street | Most grey cats are moggies, not Russian Blues. |
The dilute gene, in plain words
Colour gets into a hair in little grains of pigment. In most cats, a helper protein spreads those grains evenly along the growing hair, and the fur looks deep and dark. In 2006, researchers found that dilute cats have a broken version of the gene for that helper, called MLPH.
Without it, the pigment still gets made, but it ends up in clumps with gaps in between. Light passes through the gaps, and the eye reads the hair as paler. Same amount of black, spread badly. The result is grey.
The gene is recessive. A cat needs two copies, one from each parent, to look dilute. With only one copy it looks normal but can still pass it on, which is why two black cats can, now and then, have a grey kitten.
Blue, cream and lilac
The dilute gene doesn’t only act on black. It washes out every coat colour it meets:
- Black becomes blue, the grey you see on the street.
- Ginger becomes cream, a pale peachy beige.
- Tortie becomes blue-cream, grey and peach mixed. There’s more in tortoiseshell cats.
- Chocolate becomes lilac, a pale lavender-grey, almost never seen outside a few breeds.
So a grey-and-white cat is a diluted black-and-white, and a cream cat is a diluted ginger. Once you know it, you start seeing pale versions of every cat on your street. Lilac and other rare shades are in the rarest cat coats.
Grey tabby or solid blue?
Not every grey cat is the same grey. Look closely at the coat:
- Solid blue. One even grey all over, like the cat in the photo. This is a diluted solid black.
- Blue tabby. Darker grey stripes on a soft, warm, beige-grey background. This is a diluted brown tabby.
- Silver tabby. Black stripes on a bright, cold, silvery-white background. This one isn’t dilute at all. A different gene takes the colour out of the base of each hair instead.
Most of the “grey tabbies” you meet are one of the last two. The quick test is the stripes: dark grey on beige means blue, black on silver means silver.
The famous blue breeds
A few breeds are known for being blue, and some come in nothing else:
- Russian Blue. A bright, even blue with silver-tipped hairs and vivid green eyes. Thought to come from the port of Arkhangelsk in northern Russia.
- Chartreux. From France, blue only, with copper to gold eyes. The story that monks bred them is, the CFA says, a charming myth.
- Korat. From Thailand, silver-tipped blue and nothing else, with green eyes. Korats are a Thai good-luck cat, traditionally given to brides.
- British Shorthair. Comes in many colours, but the British Blue, with copper eyes, is the best known.
On the street, though, almost every grey cat is a moggy, an ordinary mixed cat. The dilute gene is common. Dilute cats from many breeds all share the same change, which suggests it began once, long ago, and spread with cats around the world. Your grey neighbour probably has no Russian in it at all.
Eyes to match
Grey street cats can have green, yellow, gold or copper eyes, and the grey coat makes any of them glow. In the breeds, eye colour is part of the standard: green for Russian Blues and Korats, copper or orange for Chartreux and British Blues. A grey cat with green eyes on a stone wall in Cyprus is not a Russian Blue, but it’s just as handsome.
Questions people ask
Why are grey cats called blue?
It’s the breeders’ word for it, and it stuck. A solid grey coat has a cool tone, and blue is the name cat registries use for diluted black.
Can two black cats have a grey kitten?
Yes, if both carry one hidden copy of the dilute gene. Each kitten then has a one-in-four chance of getting two copies and coming out grey.
Is my grey cat a Russian Blue?
Probably not. Most grey cats are mixed-breed moggies. A Russian Blue has silver-tipped fur, green eyes and a pedigree to prove it.
Snap the grey cats on your street. Blue, silver or cream, each one is a quiet surprise.
