This is quite a ridiculously silly question..

A red mouse is not orange. It is the same color as a red setter, a deep rust color. If anything, I'd say it's closer to brown than to orange. By "orange" I mean the color of the fruit of the same name.

Many good red mice have brown eyes because they're also cinnamon (agouti plus chocolate). The brown eyes of chocolate mice are hard to see online but if you have them against a black mouse, you can see the difference. For standards purposes, though, this kind of dark brown is "black."

For example, this mouse has brown eyes:



But for all intents and purposes, they're black.

I suspect that a mouse who was Ay/A b/b ru/ru would have pink eyes, not ruby--because both the chocolate and the ruby would lighten the eyes a small amount.

Often with reds and fawns, you'll find that the lighter (i.e. poorer) the fur color, the lighter the eyes.

No, that's not ruby eyes that people talk about when they mean ru/ru, although they may in fact be the color of a ruby (mouse terminology is confusing like that). What you're seeing is just the simple lightening of the eyes that occurs when the fur is particularly light on a yellow mouse. If you were able to breed those mice to be darker, their eyes would probably darken as their fur did. This happens on reds, fawns, recessive yellows, and American brindles as well as chocolate for reasons explained below.

These mice:





...had too-light eyes that seemed to vary under lighting conditions because they also had too-light fur.

Chocolate and the yellow-related colors are the only ones to affect the eyes in this way because they work on reducing black pigment (to varying degrees), which is in the fur and the eyes. The eyes have no yellow pigment, so when diluted, they appear red by default (you see the blood in them), as opposed to the fur which does have yellow pigment. It's often a very subtle difference on mice of varying shades, but it can make a more noticeable difference on particularly poor examples (light fur, and light eyes) of red or particularly good examples (darker fur, and darker eyes) of red. That's why the standards for red say "eye black," instead of "eye very dark brown," because on the perfect example of red (the standard), the eye is black.

The AFRMA is the only club to have standardized a color called "orange," and it's no coincidence that they allow that that eye "may be pink, ruby, or black."