My research indicates to me that some people who are interested in cats search for “grey and white cat breeds”. Although there are many cat breeds which are allowed to have grey and white coats under their respective breed standards, there are no cat breeds which must have a coat that is grey and white. Therefore there are no grey and white cat breeds.
The picture above shows the grey and white coat. The cat is a random bred cat in Japan. The photo was taken by tanakawho and published in Flickr.
A grey and white coat is a solid-and-white coat, meaning that the grey parts of the coat is solid, and the remainder is white which is without pigmentation. The colour grey in the world of cats is a dilute black which looks blue/grey. The white parts are caused by the piebald or white spotting gene.
There are 4 cat breeds which must be grey under breed standards: Nebelung, Korat, Chartreux and Russian Blue. However, there is no white in the coats of these cat breeds.
I will end there because there is nothing more to say, although I wish there was!