how dose the polygenic nature of these traits explain the wide range of phenotype

Question

Humans have a tremendous range of hair,eye,and skin colors.

Answer 1

Polygenic simply means that the trait or phenotype depends on multiple genes.  Most human traits like eye color are not determined by 1 single gene but by multiple genes.  If there are more genes involved there are more possible combinations of phenotypes/trait.

Answer 2

How did morgans research with fruit flies explain punnetts and batesons observations of pea plants?