What's the difference between these cat breeds ?

They actually look VERY different from eachother. The only way they're alike is the COLOUR of their coats. Look closer and their features and coat texture, length is actually QUITE different.

For example, the Blue British Shorthair has a very thick, plush coat, a round face, cobby body shape, smaller ears, copper eyes, a somewhat short face while a Russian Blue has a VERY short, sleek coat, a very sleek body shape and can only have emerald green eyes. One of the Chartreux's most notable features are how its ears sit right on top of its head as opposed to further to the sides like other breeds. The Korat's the only breed with a heart-shaped head and they're much smaller than these other breeds. Sure - these cats may "look he same" if you're only looking at the colour of the coat and don't have any experience in what makes each breed different.

Why are you asking this? If you have a cat with a Blue (dark gray) coat but don't have a pedigreed for it then it's none of these breeds. It's simply a "domestic" - a cat of no particular breed just like over 97% of the cats on this entire planet.

Chartreux - http://www.tica.org/public/breeds/cx/cx_a.jpg

Russian Blue - http://www.tica.org/public/breeds/rb/rb_a.jpg

Korat - http://www.tica.org/public/breeds/kt/kt_c.jpg

British Shorthair - http://www.tica.org/public/breeds/bs/bs_k.jpg

Unless you're looking at pics like these from TICA, one of the other cat registries or breeders then what you're looking at are also only blue DOMESTICS that people THINK are these breeds. They're not. And that would explain why you think they "all look the same".

There is actually a website EXACTLY for what you want!
"What Blue Cat IS That?" http://www.russianblue.info/bluecats/bluecats.htm A site comparing Russian Blue, Chartreux, Blue British Shorthair and Korat. You can look at each feature like coat, eyes, profile etc., click on photos to see closer or different views. .

It sounds like you are focusing too much on them being blue and not really looking at other features (or else as Ocimom said looking at cats who don't even come close to the breed standards) if you really think a Russian Blue looks like a British Shorthair! They are so different! the head, the body, the eyes, and actually the colour is different too. The RB's coat is silver-tipped.

OTOH, the Chartreux and a blue Brit are more similar and I can see how you could get those mixed up Chartreux has ears set higher on the head. Brits have little round wider set ears. They have a different sort of coat texture.. but can sometimes be hard to see in a photo. you have to look close. The face is different Brit is more an absolute circle. look for the Chartreux's famous smile. and the Chartreux has smaller legs.

The RB and Korat both have green eyes (but different shade of green) and silver tipped coats (but the Korat's is a single coat, the RBs is a double coat. and the Korat's is usually a darker grey)
They have quite different heads. They don't look alike to me.
But anyway that site should help you a lot..

BTW when you're learning about breeds be careful about trusting all the photos you find online in a photo search. It includes photos of domestic shorthairs /longhairs that people have mistakenly tagged as a breed. and also sometimes people take a photo of a pedigreed cat (or copy one off some other site) and then they label it as the wrong breed. I've seen a photo of a very successful Chartreux show cat belonging to someone I see at shows, turn up on some site labeled as a British Shorthair!

When looking for photos of breeds go to the sites of the registries ( CFA, TICA, ACFA have pics). or on GCCF's site theres a list of Clubs, you can find websites of clubs for the different breeds. There are Breed Clubs in US who often have websites. or CFA has a Breed Council for each breed and some have websites. Or find websites of breeders who show that breed and win.
Or there is a site called picturesofcats.org with lots of photos of cat breeds I think not 100% of photos there can be trusted but most are the professional photos by Helmi Flick and those should be really the breed they're labeled as.

http://www.breedlist.com/chartreux-breeders.html

http://www.breedlist.com/russian-blue-breeders.html

http://www.breedlist.com/russian-blue-breeders.html

http://www.breedlist.com/british-sh-breeders.html

Instead of looking at pictures you have to read the breed standards and discription.

R P CAT

I don't know where you are looking at pictures, but they must be poor quality example. Top quality cats of those breeds look NOTHING alike other then they have a blue coat.

Check out those breeds and look at the top cats from CFA winners and you should see obvious differences. It would take me too long to tell you all the differences.

http://www.cfainc.org/client/breeds.aspx

How you can tell is by their registration papers. There is not other way. Not blood work, not DNA testing or not by looking at them. If they are a breed then they will have registration papers. Other wise you are looking a a Domestic Short Hair cat or a Domestic Long Hair cat. A cat of a certain breed will be registered with a cat association. Did I explain this good enough? If you don't believe me call CFA or TICA or one of the other Associations and ask them. Also you can contact any lab that does DNA testing on cats and find out if they can tell what the breed is by blood work or DNA sample and testing. R P CAT

They have different personalitys and just different ways. There blood are all uniqe. You just need to be really interested in them