And back to Nala, her eyes are definitely much brighter green than normal in this scene, but I suspect that might be because of all the yellow hues surrounding her. It might even be a bit of artistic license on the artists' part to make her stand out even more.
I actually tried an experiment just to see whether what that "About Nala's eye color" website was proposing was legit: I opened a screengrab of Nala from one of the night scenes and one of her at the end of TLK (which is the only time we see adult Nala in full daylight) in Paint Shop Pro 7. Then I selected her pelt color from the end-of-TLK scene and adjusted the RGB values of the night scene until the pelt color in that picture was the same as the pelt color in the end-of-TLK picture. Basically, I was adjusting the colors in the night scene so that Nala would have the same colors she had in full daylight.
When I was done, the Nala in the night scene had green eyes. They certainly weren't the emerald green that they are when she is about to pounce on Pumbaa, but they weren't blue. Sea green, perhaps, but definitely not pure blue. Anyone who has Photoshop or its equivalent can try this as well.
I've seen a few people claiming that JPEG distortion made her eyes appear to be a different color. It'd be nice if someone with a very high-res monitor took a large screenshot of Nala and converted it to a PNG so the true color of her eyes wouldn't be marred by the corruptness of JPEG conversion.
Anyway, just about every official pre-SP plushie, comic, storybook, action figure, clip art, towel, sculpture, lithograph and finger puppet of Nala depicts her with green eyes, and even a good chunk of SP merchandise shows her with green eyes. Even in a storybook where her eyes are blue, the artist gives her green eyes in one picture. Because of all this, I'm inclined to think that she has green eyes. Call me crazy, but that's just the way I feel.
Still, I don't know what the artists were thinking when they not only gave Nala azure eyes, but had other characters' eyes change from blue to red and vice-versa during particularly dark scenes. Lighting does not work that way!**
And in closing, here's a little comic I did inspired by this topic (a lot of what I said here is repeated, but eh.)
*And come to think of it, Simba's eyes are more orange than red in SP...hmm...
**Zira's eyes turn blue at times during "My Lullaby" and Simba's turn blue during his nightmare.
