Mutations are every rare but do occur in some populations. There are many type of mutations but gene mutations can alter traits and cause disorders. This mutations caused color change.
4 Mechanisms of Microevolution by Marco Shields
Gene flow is when genes transfer from one population to another. For example, the red dog is going over to the white dogs affecting that populations gene flow.
Genetic drift is a change in the frequency of an allele within a population over time. There are no environmental influences that cause genetic drift to occur, but it occurs at random. Now the red dogs are becoming more dominant.
Nonrandom Mating happens when the probability for two individuals in a population will mate. When the probability is the same, then individuals are just as likely to mate with distant relatives as with close relatives. In this example the probability is equally likely.