Re: How is it possible for my half-Korean friend to have blue eyes?

Eye color and hair color are not as simple as dark over light. In general, yes, darker colors (black, brown etc.) are dominant over the lighter colors (blond for hair, blue, green for eyes). However, there are a number of genes that control the expression of eye and hair color so it isn't really a one to one correspondence of gene expression and colors. That's why there are so many different shades of eye and hair colors.

It is possible that 1) some combination of the parental gene products are producing this color. Hard to tell since it isn't known exactly how many color genes and alleles there are for eye and hair colors. 2) The mother (her egg cells) may have acquired a spontaneous mutation in her "blue-eyed" gene. 3) Some kind of mosaic expression happened. During development, instead of getting a copy of both parents' eye color genes, the child got just one parent's, in this case, just the father's. Mosaicism of this type is fairly rare but does happen. When the chromosomes in a cell are being duplicated, sometimes, the segregation of the chromosomes are uneven or don't occur properly so that one cell gets both "father" genes, the other gets both "mother" genes. All cells from then on are going to get one set or the other and if the cells are part of the optic system then that eye color will be seen.