The correct answer is : offspring with red and green cones.
Explanation:
Co-dominance follows non-Mendelian inheritance pattern. This is often caused due to the effect of multiple alleles of a particular gene, that get expressed simultaneously.
Here, unlike in Mendelian form of inheritance pattern or incompletedominance pattern where the effect of one allele of a gene is shadowed or blended by the other allele, both the alleles of the gene gets equally expressed in a heterozygous offspring.
Therefore, the heterozygous offspring show the phenotype (both red and green cones) of both the true-breeding homozygous parents (each producing red and green cones, respectively).
