Lots of possibilities really. For example, genetic drift may have operated on a population of cats thousands of years ago, bottlenecking a small sample, all of which happened to have green eyes. Subsequent 'mutations' may have brought about other eye colors. Another consideration deals with the possibility that a gene closely linked to the green-eyed trait confers some sort of advantage to cats that carry that particular trait. Dominance and ressiveness really doesn't dictate the prevalence of a particular trait. A dominant trait can be wiped out of a population simply by random fluctuation in allele frequency. It can also be replaced (in frequency) by a recessive trait that is somehow advantageous. I remember hearing some pretty striking examples of some recessive traits that have surpisingly high frequencies in populations, but none come to mind.
Edit: Here's one: dwarfism is a dominant trait.