Based on this information, what is this plant's phenotype for the fruit color trait?

 - yellow fruit
 - red fruit
The tomato plant's genotype for the fruit color gene is ff. The tomato plant's genotype of ff has only f alleles. The f allele is for yellow fruit. So, the tomato plant's phenotype for the fruit color trait must be yellow fruit.
To check this answer, consider whether the tomato plant's alleles are dominant or recessive. The allele for red fruit (F) is dominant over the allele for yellow fruit (f). This means F is a dominant allele, and f is a recessive allele.
The tomato plant's genotype of ff has only recessive alleles. An organism with only recessive alleles for a gene will have the recessive allele's version of the trait. So, the tomato plant's phenotype for the fruit color trait must be yellow fruit.