Question

if a purple flower is dominant and a red flower color is recessive how many phenotypes are possible in offsprings of homogeneous purple(PP) crossed with homozygous red(pp)

Answer 1

Since the dominant trait will always be expressed and the dominant allele is always present in this case (Pp, Pp, Pp and Pp), there is a 100% chance that all of the offspring will be purple, and therefore only one phenotype is possible. 

Answer 2

All phenotypes would be purple flowers.