I saw this link to a Nature: Nature Ecology & Evolution paper-- researchers have identified more genetic dog coats by studying the ASIP (agouti signalling protein) promoters.

Dog Coat Colors Explained By Modular Promoters of Ancient Canid Origin
There are now 2 distinct black and tan coats, plus clear yellow vs shaded yellow, and wolf grey for a total of 5 coats. Masks are separate genes, and true recessive yellow is still ee (different gene-- the dog cannot express any eumelanin). Dominant yellow will have black whiskers and black on caudal gland, etc. These genes are in order of dominance. It is not clear to me if black saddle x black back would just have an intermediate pattern between the two or not. You can see GSD (German Shepherd dog) has all colors but dominant yellow (which would be found in white GSDs only), but many shep mixes have dominant yellow. Masks and white markings are separate genes.

The paper also notes these gene variants are ancient, and one specific variant (dubbed Dominant yellow) is found in both yellow dogs and white arctic wolves... and seem to come from a different canid now extinct that diverged from wolves/dog ancestors more than 2 million years ago (which puts it nearly back to the basal canid lineage, near the golden jackal and coyote split.) They think it was introduced during hybridization of grey wolves with other canids during the Pleistocene.

https://preview.redd.it/okbjtcydm0i71.png?width=685&format=png&auto=webp&s=17ebf168b4c81c74ccbcade37ebe9fc6945b347b