The dominant seed color is yellow (Y) and the dominant seed shape is round (R). In a dihybrid self-cross between plants that were heterozygous for both seed shape (round) and seed color (yellow) i.e., RrYy with RrYy, we get 9 out of 16 seeds in the progeny that have round shape and yellow seed color.
Attachments: Punnett Square worksheet image