Answer:
Complimentary epistasis
Step-by-step explanation:
Complimentary epistatsis is the condition in which a recessive allele of one gene will mask the effect of dominant allele of other gene and vice versa. Hence, to produce the phenotype dominant alleles are required in both genes. Here.
Plant a = ccPP ( white flower since c masks the color produced by P )
Plant b = CCpp ( white flower since p masks the color produced by C )
ccPP X CCpp = CcPp
Since now dominant allele for both genes i.e. C and P are present, the progeny produced will be colored.