Heterozygous

The two alleles an individual has for a certain gene are of different varieties. For genes on the X-chromosome like the L-opsin and M-opsin, males will have only one allele, but females have two. When those alleles are the same, the female is homozygous for that gene. When the alleles are different, the female is heterozygous. Because the “colorblind alleles” are Recessive, a heterozygous female will be a carrier of Colorblindness, but not exhibit it herself.