The Chartreux is one of only two pedigree breeds (alongside the Russian Blue) genetically fixed for a single EMS color code: blue solid (a), arising from obligate homozygosity at both the Agouti locus (a/a, non-agouti/solid) and the Dilution locus (d/d, dilute), with no exceptions recognized under FIFe or any major international registry. The breed's identity is inseparable from this dual homozygous genotype, producing the characteristic blue-gray coat with the distinctive 'breakable' woolly texture; any other color phenotype arising from Chartreux breeding indicates undisclosed outcrossing or incorrect registration and is a disqualifying fault. Feline genetics programs for Chartreux are the simplest in terms of EMS color calculator scope, but breeders must remain vigilant against the introduction of non-blue alleles from any outcross or registration error.
Common recessive carriers
All Chartreux are fixed homozygous a/a (non-agouti/solid) and d/d (dilute). Unlike the Russian Blue, the Chartreux standard and historic gene pool is considered closed to outcrossing; no hidden chocolate (b) or cinnamon (bl) alleles should be present in a pure Chartreux line. The B locus should be fixed at B/B (black series) in all Chartreux, producing blue only in combination with d/d.
Breed-specific restrictions
Only blue solid (EMS: CHA a) is recognized under FIFe standard. All other colors, tabby patterns, bicolors, silver/smoke, and colourpoint variants are categorically excluded. Dominant White (W) is not permissible. Non-blue Chartreux offspring from registered Chartreux parents must trigger investigation into pedigree integrity. The breed is fully restricted to a/a + d/d + B/B genotype.
Pattern quirks
No pattern variants are accepted. Ghost tabby barring may be visible in kittens (a developmental artifact) but clears in adults. Any persistent tabby pattern in an adult Chartreux is a disqualifying fault indicating hidden agouti (A/-) allele. Smoke and silver phenotypes are not recognized and would indicate a non-Inhibitor-fixed population issue.
CHA aBlue (solid) — the only recognized color for the ChartreuxFree online tool to predict kitten coat colors based on Mendelian genetics. Select the breed and appearance of sire and dam to see color probabilities.
Enter the appearance of both parents to calculate color predictions.