What is rarest combination of hair and eye color?

The rarest combination of hair and eye color is red hair and blue eyes. Both red hair and blue eyes are caused by recessive genes, meaning that both parents must carry the gene in order for their child to have red hair and blue eyes. This combination is particularly rare because there are very few people who carry both recessive genes. In fact, red hair and blue eyes make up less than 1% of the world's population.