I'm going to assume you are using a strong definition of the word "realistic".
Anyway...
The crux of the idea is to exploit something along the lines of a tapetum lucidum. Having done a little research (Wikipedia), it seems that the majority of so-called eye-shine phenomena in vertebrates stems from the presence of crystalline inclusion bodies in the cells behind the retina. Colors vary from species to species, so, presumably, with crystals built from the correct proteins, you could get the color you want.
As for making the eye-shine emotion-dependent, I see several possibilities.
The tapetum could be only mildly reflective, weak enough that noticeable eye-shine would only occur when the character's pupils were widely dilated — something that often occurs during moments of intense emotion.
The crystalline inclusion bodies in the cells of the tapetum could be contained in contractile vacuoles. The reflective pigments/crystals would only be exposed when the vacuoles are expanded, which could occur as a simple stress response (triggered by acetylcholine, or whatever).
