Rare French Bulldog Colours Explained: Blue, Lilac, Merle, Isabella and Fluffy

The rare French Bulldog colours you see advertised (blue, lilac, isabella, merle and the long-coated "fluffy") are not rare in nature so much as outside the breed standard. Dogs Australia and the UK Kennel Club recognise only brindle, fawn and pied (with whites shown as pieds), and every "rare" colour comes from a recessive or introduced gene that breeders have to deliberately stack. Some of those genes are harmless to the dog. Others, merle in particular, carry real health risks, so it pays to understand the genetics before you fall for a coat.

What colours does the French Bulldog breed standard allow?

In Australia the breed standard is published by Dogs Australia (the ANKC). It says the only correct colours are brindle, fawn and pied.¹ Brindle is a mix of black and fawn hairs. Fawn can have or not have a black mask, and cream and red shades are described as "less desirable". Pied means white predominates with brindle or fawn patches, and all-white dogs are classified with pieds for showing.¹

The same standard spells out what falls outside it: solid black, black and white, black and tan, mouse, grey/blue, liver/chocolate "and all patterns of these colours" are listed as highly undesirable.¹ The UK's Royal Kennel Club standard is stricter in its wording and simply states that any other colour or combination is unacceptable.²

In the US, the French Bull Dog Club of America's interpretation of the AKC standard accepts brindle, fawn, white and brindle-and-white, and lists solid black, mouse, liver, black and tan, black and white, and white with black as disqualifications. "Blue" counts as mouse.³

So a blue or lilac Frenchie can be a lovely pet. Its "rarity" just isn't a mark of quality.

Rare French Bulldog colours and the genetics behind them

Several genes work together to set coat colour. The four that matter most for "rare" Frenchies are:

• D locus (dilution, MLPH gene): recessive. Two copies (d/d) lighten black pigment to blue/grey and brown pigment to lilac.⁴
• B locus (brown, TYRP1 gene): recessive. Two copies (b/b) turn black pigment into brown. Breeders often call this "testable chocolate".^5,6
• Co locus (cocoa, HPS3 gene): recessive. A second, separate brown found in French Bulldogs. Two copies (co/co) give a slightly darker brown. Before a DNA test existed it was nicknamed "non-testable chocolate".^5,6
• M locus (merle): dominant. One copy is enough to create the marbled merle pattern, and two copies cause serious problems (more below).^7,8

Blue French Bulldog

A blue French Bulldog is genetically a black-pigmented dog with two copies of the dilution gene. Because dilution is recessive, both parents must carry at least one copy.⁴ Blue is the colour most often linked with colour dilution alopecia, which we cover in the health section.

Lilac French Bulldog

"Lilac" is a pale, greyish-lavender coat. In the Frenchie world it usually means a cocoa dog that is also diluted (co/co plus d/d). The researchers who identified the cocoa gene found 47 of 48 brown or lilac French Bulldogs they tested carried two copies of the cocoa variant.⁵

Isabella French Bulldog

Isabella is the name Frenchie breeders use for diluted testable chocolate (b/b plus d/d), while lilac generally refers to diluted cocoa.⁶ The two shades can look almost identical, and one genetics reference notes they can be very hard to tell apart without testing.⁶ Treat these names as breeder shorthand: only a DNA report tells you what a puppy really is.

Merle French Bulldog

Merle creates patches of diluted colour over a darker base and often blue or odd-coloured eyes. It is caused by a dominant gene, so only one parent has to carry it.⁸ The Royal Kennel Club refuses to register merle French Bulldogs at all, because there is no documented history of the colour being established in the breed and because of the hearing and sight risks linked to the merle gene.⁷

Fluffy French Bulldog (long-haired)

Fluffy isn't a colour. It's a coat length, caused by recessive variants in the FGF5 gene. In French Bulldogs two variants, known as L1 and L4, can produce a long coat, and a puppy needs two long-hair copies to look fluffy.⁹ That's why long-haired Frenchies are genuinely uncommon: both parents must carry the gene. The breed standard calls for a short, fine, smooth coat,² so fluffies can't be shown. We go much deeper in our guide to long-haired French Bulldogs.

French Bulldog colours at a glance

Colour or coat	Simplified genetics	In the Dogs Australia standard?	Health notes
Brindle	Black and fawn hairs mixed	Yes	No colour-linked issues
Fawn (with or without mask)	Fawn base; cream and red less desirable	Yes	No colour-linked issues
Pied / white	White predominates with patches	Yes (whites shown as pieds)	Pink skin under thin white hair is prone to sunburn
Blue	d/d (dilution)	No ("grey/blue" highly undesirable)	Risk of colour dilution alopecia
Chocolate (testable)	b/b (TYRP1)	No ("liver/chocolate")	None well documented in Frenchies
Cocoa	co/co (HPS3)	No	Platelet changes found in a study; no major health problems seen so far
Lilac	co/co + d/d	No	Dilution: risk of colour dilution alopecia
Isabella	b/b + d/d	No	Dilution: risk of colour dilution alopecia
Merle	M (dominant)	No (not registrable in the UK)	Hearing and sight risks; double merle (M/M) much worse
Fluffy	Two long-hair FGF5 copies (L1/L4)	No (standard calls for short coat)	Extra coat needs grooming; no specific disease link documented

Are rare French Bulldog colours unhealthy?

It depends on the gene, plus one bigger issue that applies to all of them.

Colour dilution alopecia (blue, lilac, isabella)

Colour dilution alopecia is an inherited, recessive condition linked to dilute coats. VCA Animal Hospitals explains that puppies are born with a normal-looking coat, then from around six months of age or older the hair thins, usually starting along the back, and the skin can become scaly, itchy and prone to small bacterial infections.¹⁰ It isn't curable, but it is manageable with medicated shampoos, rinses and sometimes antibiotics, and affected dogs (and their parents and siblings) shouldn't be bred from.¹⁰ If your blue or lilac Frenchie starts thinning or getting flaky, see your vet. Our post on sensitive skin in dogs covers the day-to-day care side.

Cocoa and the HPS3 gene

The cocoa gene is linked to bleeding and vision problems in people and mice, so researchers looked closely.⁵ A 2021 study of French Bulldogs found cocoa dogs had fewer of a particular type of platelet granule, but owners reported no increased bleeding in daily life, and the authors concluded the effect appears largely limited to coat colour, while calling for more study.¹¹

Merle and "double merle" French Bulldogs

This is where the stakes are highest. A dog with two copies of merle (M/M, a "double merle") comes from mating two merles together. These dogs are often very pale or mostly white and can have developmental defects including small, malformed eyes and hearing loss.⁸

A study of 153 merle dogs across ten breeds found deafness in 3.5% of single merles but 25% of double merles, with 15% of double merles deaf in both ears.¹² That's why the Royal Kennel Club restricts registration of puppies from two merle parents,¹³ and why no ethical breeder will ever mate merle to merle. Both parents should be DNA tested for the M locus so there are no surprises.

The bigger problem: breeding for colour first

The UK Kennel Club has warned that breeders producing unrecognised colours often show "little or no regard" for health, temperament and conformation, that some mislead buyers by calling colours "rare", and that the French Bulldog is the breed most affected by the trend.¹³ When the gene pool gets narrowed down to whichever dogs carry blue, cocoa or merle, health screening can slide down the list.

That matters because Frenchies already have plenty to contend with. A Royal Veterinary College VetCompass study of 2,781 French Bulldogs found they had higher risk than other dogs for 20 of 43 common disorders, including narrowed nostrils (over 42 times the risk) and brachycephalic obstructive airway syndrome.¹⁴ A healthy airway matters far more than coat colour.

Why do rare French Bulldog colours cost more?

Mostly supply, demand and marketing. Blue, chocolate, cocoa and long hair are all recessive, so both parents must carry the right genes, and "stacking" several (as with fluffy lilac) takes more planning. Social media made those looks fashionable, and "rare" sells, but as the Kennel Club notes, the label is sometimes used to mislead buyers.¹³ A higher price is not a sign of a better-bred dog.

How to find an ethical French Bulldog breeder in Australia

Whatever colour you love, the checklist is the same:

• Ask for DNA reports for both parents, covering colour genes (especially merle) and breed health tests.
• Ask for BOAS grades. Dogs Australia is rolling out the Respiratory Function Grading Scheme developed by the University of Cambridge and the UK Kennel Club, with trained vet assessors appointed in several states.¹⁵ Dogs are graded 0 (no signs) to 3 (severe), can be assessed from 12 months and are retested every two years while breeding.¹⁶ Dogs Australia lists the French Bulldog as a high-risk breed, with only about 10% grading 0,¹⁷ so ask for the parents' actual grades.
• Meet the mother where the puppies were born. RSPCA Queensland recommends buying directly from the place a puppy was born so you can see the parents and how they are kept, and warns against breeds bred for exaggerated features.¹⁸
• Check rescues too. RSPCA Queensland suggests looking at rescue groups before going to a breeder.¹⁸

Pied and white French Bulldogs in the Aussie sun

Pieds are fully standard, but they have their own care point. White hair over pink skin gives little protection from UV, and RSPCA South Australia warns that white-haired pets are prone to sunburn and skin cancer, mostly on thinly furred areas like the nose, ears and belly.¹⁹ Its advice is to limit midday sun, use a pet-safe sunscreen on exposed spots and see a vet quickly if skin looks red, scabby or sore.¹⁹ Our guide to whether dogs can get sunburn covers this in detail, and if your pied Frenchie loves the beach, a UPF 50 rated rash shirt helps reduce UV exposure on the back and belly (more in does my dog need a rash shirt?). Whatever the colour, Frenchies need extra care in hot weather, so brush up on keeping a French Bulldog cool in summer.

FAQs

What is the rarest French Bulldog colour?

There's no official ranking. Combinations that need several recessive genes at once, such as fluffy lilac, are the least common, but that rarity comes from deliberate gene stacking, not anything special about the dog.

Are long-haired French Bulldogs rare?

Yes, relatively. A fluffy Frenchie needs two copies of a recessive long-hair (FGF5) variant, one from each parent, so both parents must carry it.⁹ Long hair isn't in the breed standard, which calls for a short, smooth coat.²

Can a blue French Bulldog be registered with Dogs Australia?

The Dogs Australia standard lists grey/blue as highly undesirable, so a blue Frenchie won't do well in the show ring.¹ If papers matter to you, ask your state's Dogs Australia member body about registration rules for non-standard colours before buying.

What's the difference between lilac and isabella French Bulldogs?

Both are diluted brown. Lilac usually means diluted cocoa (co/co plus d/d), while isabella means diluted testable chocolate (b/b plus d/d).⁶ They can look almost identical, so only a DNA test tells you which one you have.

Is a merle French Bulldog healthy?

A single merle can live a normal life, but the merle gene is linked to higher risks of hearing and sight problems, especially with two copies.^7,12 Never buy from a breeder who mates merle to merle, and ask for M-locus DNA results for both parents.

Do blue French Bulldogs lose their hair?

Some do. Blue and other dilute dogs can develop colour dilution alopecia, usually from around six months, with thinning hair and flaky skin.¹⁰ It's manageable but not curable, so see your vet if you notice changes.

References

1. Dogs Australia, French Bulldog breed standard
2. The Royal Kennel Club, French Bulldog breed standard
3. French Bull Dog Club of America, Color (interpretation of the standard)
4. Genomia, Locus D canine (dilution, MLPH)
5. Kiener S et al. (2020), Novel Brown Coat Color (Cocoa) in French Bulldogs Results from a Nonsense Variant in HPS3, Genes
6. Coats and Colors, Cocoa locus
7. The Royal Kennel Club (2020), Registration of dogs of merle colouring
8. Hédan B et al. (2006), Coat colour in dogs: identification of the merle locus in the Australian shepherd breed, BMC Veterinary Research
9. Eurovetgene, Coat length (FGF5, L1)
10. VCA Animal Hospitals, Color Dilution Alopecia in Dogs
11. Laukner A et al. (2021), Effects of cocoa genotypes on coat color, platelets and coagulation parameters in French Bulldogs, Genes
12. Strain GM et al. (2009), Prevalence of Deafness in Dogs Heterozygous or Homozygous for the Merle Allele, Journal of Veterinary Internal Medicine
13. The Royal Kennel Club (2017), Kennel Club addresses issue of unrecognised colour registrations in pedigree dogs
14. Vet Times (2021), Frenchies "no longer a typical dog" – RVC
15. Dogs Australia, Respiratory Function Grading Scheme
16. Dogs NZ, Respiratory Function Grading Scheme
17. DOGS NSW (2026), From Dogs Australia: Updated list of breeds that can be assessed under the RFG scheme
18. RSPCA Queensland, What you need to know when buying a pet
19. RSPCA South Australia, The must-know steps to keeping your white pet safe from dangerous sunburn