Incomplete dominance is when the phenotypes of the two parents blend together to create a new phenotype for their offspring.
Co-dominance is a relationship between two versions of a gene.
Therefore, In complete dominance, only one allele in the genotype is seen in the phenotype. In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.