If you selected a grey seeded plant in the F2 generation how would you determine if the plant is homozygous or heterozygous?

Depending on the F1 generation (parent) phenotype we can determine whether or not it is homozygous or heterozygous. Also, check to if the F2 grey seeded plant is a mixture of Black and white or if grey is a dominant color. If it is a mixture, it would make it heterozygous. If not and Grey is domminant it would make it homozygous.