You can tell by the head shape.
The head of Saudi blue cat is round and big, and it is slightly bigger than other blue cats. British blue cat is also the most common, which is a variant of British short-haired cat. However, because of its blue-gray hair, it has such a name. This male cat has a small head and a gentle personality, and is particularly dependent on its owner. Russian blue cat's limbs are slender, elegant, thin and its head is not that long.
Distinguish by the color of the eyes.
Bian Xiao also mentioned before that chartres Blue Cat's eyes are dark, yellow or copper yellow, even reaching orange. So if you see the color of the male cat's eyes like this, you can tell that its breed is chartres. British blue cats have lighter eyes, one is light yellow, and their eyes are softer. This cat's legs are short and thick, and it is also called English short-legged blue cat. Russian blue cats have yellow-green eyes and gray or blue-gray fur. This kind of cat's hair is particularly thick to adapt to cold weather.
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Among them, chartres blue cat and English short-legged blue cat are difficult to distinguish, mainly by observing their mouths. Chartres's mouth is downward, and the short mouth protrudes forward, with a small upward arc.