I've never heard of such a test. Do they only do it in Iceland?
Because if she is, in fact, a cremello in our terms, she does have genes to pass on. Each parent has 2 copies of a gene, with one being passed from each parent to the offspring. If she's a cremello, she will always pass on the Cream gene. She will also only pass on the red gene, which is recessive to black.
But if such a test exists, it would be highly interesting to me and some others and I'd love to look more into it.