In dogs, gum coloration is co-dominant, with black coloration,
black & pink spotted and pink.
you have a lovely spotted gummed labrador retriever who has
just had 8 pups. four of the pups have spotted like your dog.
and 4 have pink gums.
what is the likely phenotype of the sneaky neighbor dog? show
your work.

The phenotype of the sneaky neighbor dog will be pink. Let's consider the phenotype of our spotted gummed Labrador to be CPCB and neighbors dog to be CPCP

          CP          CB

CP     CPCP       CPCB

CP     CPCP      CPCB

The results of this cross show that there will be a probability of having pink dogs as well as spotted dogs. Hence, this proves that the neighbors dog had pink gums.