In reference to garden peas, Gregor Mendel, the father of genetics learned that the allele for the color green is dominant to the allele for the color yellow. One can use the letters capital G to represent the dominant color green, and lower case g, to represent the recessive trait yellow. Therefore, if an offspring's genotype is GG, then it is said to be homozygous green. If the genotype of the offspring is Gg, it is heterozygous, but still green as the color green is dominant to yellow. If the offspring is homozygous gg, then, it will be the recessive yellow color. Finally, the only genotype to produce a yellow colored pea plant, is to have the homozygous gg genotype.
In addition to what I answered above, since you were not specific in your question, the trait of green pea pods is dominant to yellow pods, however the trait of green peas is recessive to yellow peas. In the answer above, I assumed you meant the pea pods, not the pea seeds.