Offspring: 25% SS(Standard Grey) 50% Sc(Standard 100% color hets) 25% cc (Color)
Of the Standard Grey offspring, 2 out of 3(2/3 or 66%) would be hets & 1/3 would not. For this reason, Standard Grey joeys out of a 100% x 100% cross are listed as 66% hets because they have a 66% chance being a carrier of the recessive color gene.