In parakeets, feather color is determined by two independently assorting genes. The blue/black pigment (melanin) is produced in feathers when the dominant allele (C) is present. A yellow pigment is also produced when another dominant allele (B), on other chromosomes, is present. These pigments are not produced when their respective recessive alleles (c and B) are homozygous.
This results in four different colors of parakeets: green (B-C-), yellow (B-cc), blue (bbC-), and white (bbcc). What color offspring, and in what ratio, would be expected from a cross between a white parakeet and a dihybrid green parakeet?