"New shade Isabella carrier" refers to a dog that carries a specific genetic trait that causes a new variation of the Isabella coat color. New Shade Isabella is a rare coat color that is a light champagne color. A carrier of the New Shade Isabella gene does not have the coat color themselves, but they carry the gene and can pass it on to their offspring. This means that if a carrier is bred with another carrier or with a dog that has the Isabella coat color, some of the puppies produced in the litter may have the new shade Isabella coat color.
It could also mean that the dog might carry a new genetic mutation of the New Shade Isabella gene which might result in an unusual or new shade of Isabella coat.