Question

If an orange pet mates with another orange pet, can they have any green offspring?

Answer 1

depends on the breed of the animal although possible it depends on the genes

Answer 2

Yes. Say the orange allele is dominant to green and call the allele O. If the parents were both heterozygous, or Oo and Oo, they would be orange. In a cross, they have a 1/4 chance of producing oo, or green.