The DNA Help Eye Colour Inheritance Chart is based on a theory that dates back to the 1800's. In only very rare cases can it be used to predict possibilities of paternity. The calculator is used to determine either: The possible eye colours of the child when the eye colours of the mother and the father are known. The possible eye colours of the father when the eye colours of the mother and the child are known. Eye colour is known to have a polygenic inheritance pattern, possibly governed by 6 or more genes. There are also 6 different described eye colours. Basically, dark is dominated at each of the 6 genes, and the more dominate alleles that you have the darker your eyes are. The different eye colours and number of dominate alleles suggested in this theory are seen below. DNA Help Eye Colour Inheritance Chart: Light blue 0 dominate alleles Blue 1 dominate alleles Blue-green 2 dominate alleles Hazel 3 dominate alleles Light brown 4 dominate alleles Brown 5 dominate alleles Dark brown / black 6 dominate alleles Basically, based on this theory: 2 'light blue' eyed parents cannot have a 'blue' eyed (or darker eyed) child. 2 'blue' eyed parents can have a 'Blue-green' (or lighter) eyed child, but not hazel or anything darker. 2 'blue-green' eyed parents can have a 'Light brown' (or lighter) eyed child, but not brown or anything darker. 1 'Light brown' eyed parent and 1 'blue-green' eyed parent can have a child with any of the possible eye colours. 2 'dark brown or black' eyed parents can have a child with any of the possible eye colours (but it is unlikely they will have a light eyed child, such as light blue or blue). Lastly, before jumping to conclusions, eye colour usually starts out much lighter at birth, and becomes its true colour in 1 or 2 years after birth. Variations can also occur randomly. Interestingly, this theory was generated in the late 1800's, which demonstrates, 1) how inheritance patterns were pretty well understood (by some) back then, and, 2) that eye colour is, still today (even with the human genome sequenced), very difficult to predict due to its polygenic inheritance pattern. In conclusion, eye colour is not a very reliable or accurate method to use when attempting to determine paternity of a child.