There is three different states (genotypes) shown in this pedigree:
-Homozygous dominant (AA) which phenotype is a yellow color, and it is represented by a blank fill.
-Homozygous recessive (aa) which phenotype is a red color, and it is represented by a red fill.
-Heterozygous (Aa) which phenotype is a yellow color, but it is a carrier of the recessive allele red that is "hidden" behind the dominant allele and it is not shown phenotypically. These individuals are represented by a fill half blank and half red to highlight the genotype.
Therefore, in order to determine which is the genotype of the individual IV-5, is important to analyze the alleles that it obtained from its parentals.
-Individual III-8 is fully red, so its genotype is aa. It can only give "a" alleles.
-Individual III-9 is fully blank, so its genotype is AA. It can only give "A" alleles.
Therefore, as children obtain one allele from each parent, the only genotype possible of IV-5 is "Aa", i.e heterozygous, which is represented by half fill blank and half fill red, and its phenotype is yellow.