“…a deep gray with dark ticking/heathering and black guard hairs…”

The D Locus

Russian Blue is a recessive gene that derives it’s namesake from the cat breed, of which it, mice and many other animals dilute gene share similar appearances with. When it was first discovered it was actually known as “Mouse Blue” but was changed soon after. The UK terminology is Rb as D was already being used for the other blue locus. It is a deep gray with dark ticking/heathering due to uneven pigment distribution in the singular hair strands as well dark guard hairs, giving it a distinct appearance from similar blue mutations. The coloring doesn’t vary much, and as such does not come in extreme light or dark shades. They can however vary from a even bluish grey to having a brown cast (which is usually seen as a fault). Their coloring is consistent down to the skin. Russians also do not tend to silver as much which is extremely common in other blue genes.


In 1993 Geri Hauser adopted and breed three silver-biege rats from Karla Barber Velvet line, a breeder in the California area. She was surprised to find that the kittens were of a unique dark gray similar to mice and cats that had yet to be seen in the fancy. While first naming them “Mouse Blue” they were soon renamed to “Russian Blue” after the popular breed of cat. The

How ever due to the fact that many pet stores and backyard breeders claimed to be selling Russian Blue that we’re actually slate blue to capitalize off the popular trend in the cat breed, there was and still to some extent is to this day a large confusion in Blue and Russian Blue lines being mislabeled as one another.

It was first shown in 1994, and shortly thereafter in 1996 was standardized.


The Dilute mutation has a variety of combinations that are both stunning and quite popular among fancy rat owners and breeders. Many of these are similar to the combinations made with slate blue but darker. Russian is popular among the pointed varieties as well, and tends to be the preferred gene for color locus variations. Dove is another popular variety by combing it with the mink or chocolate gene. Of course crossing with the Grey locus creates the stunning Silver Blue/Russian Silver or Silver Dove in combination with Dove.


            AFRMA [US] 

RUSSIAN BLUE –  Color to be similar to the blue mice or blue cats, a very dark slate blue color with dark ticking throughout. Eyes black.


RUSSIAN BLUE – Like the Russian Blue cat–very dark slate blue with dark ticking throughout, black eyes.


RUSSIAN BLUE – Colour to be similar to blue cats and dogs. A soft medium grey-blue with a metallic sheen. Faint, light speckling or a subtle ticked effect (heathering) is usual for this variety and is not a fault. Colour to be even, belly colour to match top. Undercolour dark blue down to skin. Coat to be short and thick- a long coat or a coat similar to that on other varieties (excluding rex) to be a serious fault. Eyes black.












  • The D-Locus is recessive.
  • They have little variation and absent of other dilution genes produces very similar colored rats.
  • The distinctive coloring comes from heathering in the individual hairs.
  • Russian Blue is a very popular coloring, but can sometimes be mislabeled blues.

A Final Thought

Russian Blue is a more typical blue dilution being more similar to other animals blue dilutes then the rats first blue mutation on the g locus. It is widely as popular as the other shades of blue and offers some unique cross genetics that stand out stronger on the c locus responsible for Siamese, Himalayan and Marten. It’s deep steel coloring has a striking sheen that is sure to turn heads.