<p>I have to admit I don't know much concretely about eye color, but I am happy to speculate.</p>
<p>I found a [url=<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16280011&query_hl=6&itool=pubmed_docsum%5Dpaper%5B/url">http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16280011&query_hl=6&itool=pubmed_docsum]paper[/url</a>] which I'm referencing here. (Can you see it from that link?) The citation is
Wielgus AR, Sarna T. "Melanin in human irides of different color and age of donors." Pigment Cell Res. 2005 Dec;18(6):454-64.</p>
<p>Color in the ring around the pupil is caused by the relative amount of a pigment protein called melanin (the same stuff that makes moles and freckles brown). People who have more melanin (= more or more productive melanin-producing cells) have brown eyes, while people with very little melanin (= fewer or less productive melanin producing cells) have blue eyes. There are several other sources of color variation: melanin comes in a few different forms (pheomelanin and eumelanin, and probably others), and color can be modulated by iron molecules in the eye.</p>
<p>
[quote]
It appears that the iris color fully develops during infancy.... pigment production is not normally observed during later stages of organism development. Thus, the characteristic color of the eye... does not change significantly during the lifetime. This should not lead to a conclusion that melanin content and/or its structure do not undergo any changes at all. Indeed, some epidemiological studies suggest that the human irides become lighter at older age.
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</p>
<p>So it seems like what's happening is that there's variation in the production of melanin, both across the area of the iris (in atmjunk's case) and in time (in ariesathena's). The reason for this is probably complicated, and can't be well-described by just referring to dominant or recessive genes. Basically, for whatever reason, the genes for melanin are transcribed at different frequencies at different times/areas of the eye.</p>