The blue lynx is an extremely rare variant of the Canada Lynx, a medium-sized wild cat species living in Canada and in certain parts of North-West America.
The diluted coat color is due to a genetic mutation. In 1938 the skin of a Canada lynx was obtained from Alaska and donated to the US National Museum.
The cat’s coat was of a bluish-grey color instead of the usual fawn. According to the fur traders in the region where the cat was found (trapped I presume) such mutants with their dilutant coat-coloured gene occur once or twice in every thousand cats (pelts in this case because the information comes from trappers).
It seems that the gene which causes diluted colors in the cat’s coat and which is present among domestic cat is also expressed, rarely, among wild cats. A dilute version of black is the blue coat for instance. There is such a cat as a black bobcat by the way. Bobcats are in the same family of cats as the lynx. Blue tigers were present in the wild at one time.
I don’t have a photograph. Google is completely dumbfounded by a search for ‘blue lynx cat’.
Source: Dr Desmond Morris – Cat World page 62.