What is the best explanation for how we can exhibit so many different traits from so few genes

Alleles of a gene are responsible for different traits

Explanation:

There are several variant of a gene which in pair leads to varied phenotypic characteristics or traits.

For instance, there are three alleles for blood group i.e A, B and O but there are in totality there are basic 8 blood groups including the categorization on the basis of Rh factor.  

Likewise, there are several variations of skin color; however there are majorly six genes that are responsible for skin color.  

So, basically alleles of a gene are responsible for different traits

b is dominant over the allele for the white fur.