Answer:
According to the given question that without prior knowledge on the prodigiosin synthesis pathway of these Serratia species, and we experience two different color morphs of the species. So, there is given or known preliminary morphological basis we will consider them different two different colonies. These can be identify only after genetically identify or study.
The morphological characterstics of the organism and the genetic identification both are equally important. So Giving any one more importance over other is not logical.
Morphologically we can differentiate the color of the colonies of mutants. The mutant serratia sp. are known for eficient biosynthesis of prodigiosin, Thus on the basis of color characteristics of their colonies when grown on peptone glycerol medium we can identify.