Codominance in coat colors of palomino horses

D1 and D2 are a pair of codominant alleles involved in the inheritance of coat colors in horses. Genotypes homozygous for D1 produces chestnut [reddish], heterozygous genotypes palomino [golden color with lighter shade of mane and tail] and homozygous for D2 cremello [almost white].

a) Determine the probable palomino: non-palomino ratio amongst the offsprings of palomino only matings.

b) what percentage of the non-palominos can be expected to breed true?

c) what types of matings would produce only palominos?