We can only recommend you to take your kitty to the vet. It seems like s/he still has an appetite, which is a good sign, but panting might be an indicator for something else. Are there any other signs of discomfort? Salivating or does s/he have blue gums? Whether yes or no, you might want to go get a check-up to make sure everything is safe. A veterinarian will know how to guide you and recommend treatment if there is an underlying medical issue. Best of luck!
Solid black Chausies may have faint tabby markings (called ghost markings) as kittens, but usually acquire a dense, even black pigmentation with maturity. Sometimes black grizzled tabby Chausies will appear indistinguishable from solid black Chausies when the amount of grizzling is minimal. Exposure to strong sunlight, as with most black cats, can cause black Chausies to lighten slightly and appear brownish.
A British cat fancier named Mrs. Carew-Cox began importing the cats in 1890 and bred and showed them through the turn of the century. She described them as having short, silvery fur, large ears, wide-set eyes and lean faces, with sweet, intelligent personalities—in short, much the same as the Russian Blue of today. In 1912, the cats were well enough established that they could be shown in a class of their own instead of being lumped together with other blue cats.
There are various different causes for rapid breathing which may include infections, pain, heart disorders, dehydration among other causes; a cat’s respiration should be below 30 breaths per minute when at rest but if it is significantly above this rate at rest I would suggest visiting your Veterinarian for an examination to determine a cause. Regards Dr Callum Turner DVM