I found this link interesting:
Eye Shine
"The eye in all animals except pigs and man have a reflective layer along the back of the retina called the tapetum. This layer serves to reflect light to allow maximal usage of the available light. In some animals the tapetum is colored in others it is not.
The reddish color that you see in human eyes is the reflection of the blood vessels in the back of the eye because the tapetum is NOT colored. This is the same in the "red eye" of the Yorkie.
The blue and green you see in the Yorkie's are from a pigmentation in the tapetum -- how this relates to coats I am not sure.....but could be that pigmentation of the eye and coat texture are related genetically. Tapetums are very beautiful -- metallic, brilliant colors in most animals.
You can watch Yorkies, clipped down or in full coat, outside in the sunshine ... and you can easily separate them into two groups - those with a "blue cast" to the coat, and those with a "gold cast" to the coat.
Those with gold or bronze cast to the coat have eyes that reflect a flash bulb or flashlight with the "red eye" or "shiny" red reflection to the pupil.......no pigment.
Those blue cast dogs always seem to reflect blue or green from the pupil.....pigment.
The "red eye" dog has a thicker, softer, more opaque (not shiny silky) coat ... silky coated pups look kind of straggly."