Russian Blue — Color Genetics & EMS Calculator

The Russian Blue is genetically defined by absolute restriction to a single phenotype: blue solid (a/a + d/d), representing homozygosity at both the Agouti locus (non-agouti, a/a) and the Dilution locus (d/d), producing a uniformly diluted, non-patterned coat. This mandatory dual homozygosity means that any Russian Blue carrying a dominant allele at either the A locus (A/-) or D locus (D/-) cannot express the breed-defining phenotype and is a disqualifying fault in FIFe and most major registries. Feline genetics and EMS code calculator tools for RUS are therefore minimally complex at the color level, though breeders must still genotype for hidden chocolate (b) alleles that — while not expressed in the all-blue standard — must not produce non-blue offspring.

Russian Blue colour genetics: frequently asked questions

Which recessive colours do Russian Blue cats commonly carry?
All Russian Blues are fixed homozygous d/d (dilute) and a/a (non-agouti/solid). Chocolate (b) alleles are reported as present in some RUS lines; while b/b would produce chocolate, no b-series dilutes (lilac, etc.) are accepted. Any non-blue phenotype arising from a Russian Blue pairing indicates either a registration error or undisclosed outcrossing and is a disqualifying fault.
What colour restrictions apply to the Russian Blue breed standard?
Only the blue solid phenotype (EMS: RUS a) is recognized under FIFe standard. All other colors — black, white, colourpoint, tabby patterns, silver, bicolor — are categorically excluded. Russian White and Russian Black are recognized as separate varieties in some non-FIFe registries (e.g., CCCA in Australia) but are NOT valid under FIFe. The breed is strictly fixed for a/a (non-agouti) and d/d (dilute) genotypes.
Which coat patterns are typical for the Russian Blue?
No pattern variants are accepted. Although ghost tabby striping may be faintly visible in kittens (a transient phenotype from residual phaeomelanin during development), adult Russian Blues must present as solid blue with no visible tabby pattern. Smoke, silver, bicolor, and white-spotting are all disqualifying.

Popular EMS Colors

RUS aBlue (solid) — the only recognized color
RUS a (kitten)Blue solid — note: ghost tabby barring in kittens is genetically non-agouti (a/a) and resolves with maturity

Calculate Colors for Russian Blue

Free online cat color genetics calculator. Select the breed and appearance of the sire and dam to predict kitten coat colors, patterns and probabilities based on feline color genetics.

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