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)

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.

All phenotypes would be purple flowers.