What Are Genetics Of Eye Colour?

These are actually very complicated.  There may be dozens of genes involved in eye colour.  This helps to explain the subtle ranges of shades of blue, brown, green and hazel that are seen.  There also seems to be a relatively high rate of spontaneous mutation in the genes associated with eye colour. This is partly why some families with no apparent history of eyes being a particular colour (say, blue) might have a blue-eyed baby.

There are simple rules that do influence the statistical likelihood of which colour will appear in one's offspring, but these rules aren't hard and fast (not least because of the possibility of mutation).  Black or brown eyes generally dominate blue eyes, and blue generally dominates green.  There are two main genes for eye colour that have been well studied.  Gene One can be either green or blue; Gene Two an be either brown or blue.  In most cases, if one of the two copies of Gene Two that you inherit from your parents is brown, then brown will be your eye-colour... but not always.  Brown isn't always dominant.  In theory Green eyes should never occur... but they do.