Final answer:
A heterozygote for seed coloration gene refers to the organism's genotype, which comprises the entire set of genes including the alleles that the organism has inherited.
Step-by-step explanation:
A heterozygote for seed coloration is a reference to an organism's genotype. The term genotype refers to the genetic makeup of an organism, including all the genes and alleles it carries, whether expressed or not. A heterozygote has two different alleles for a particular gene. On the other hand, phenotype is the set of observable characteristics of an organism, which results from the interaction of its genotype with the environment.
For example, in Mendel's pea plant experiments, seed color was an observable trait, or phenotype, which was influenced by the underlying alleles (the genotype). When Mendel crossed a true-breeding yellow-seeded plant with a true-breeding green-seeded plant, the F1 offspring were heterozygous with one yellow and one green allele, but all exhibited the yellow seed phenotype due to the dominance of the yellow allele.