Additive Alleles Mastering Genetics

Two pure-breeding wheat strains, one producing dark red kernels and the other producing white kernels, are crossed to produce F1 with pink kernel color. When an F1 plant is self-fertilized and its seed collected and planted, the resulting F2 consist of 160 plants with kernel colors as shown in the table.


Kernel Color   Number
White               9
Dark red              12
Red                      39
Light pink              41
Pink                      59

How many additive alleles are required to explain the five phenotypes seen in the F2?
    2
    1
    8
    4

Im thinking the answer is 2 but im not sure.