Can eyes change color?

[FinFan]

I've been wondering about this for ages, but it's just slipped my mind every time. I've had my betta for nearly a year now, and since day one, his eyes have been black. But here's the weird part - at night, they change to this really pale icy blue color, almost white. By morning, they're back to black. Anyone have any idea what's going on with my betta's eye color?

[juicebox]

I think it's possible that the lighting is playing a role here. Pupil dilation could also be a factor, I'm not entirely sure if that's the correct term or if it's even applicable in this situation, but it's worth considering.

[juicebox]

Can you take a couple pics of Fluxx, one during the day and one at night, and post them here?

[CasCat]

My betta boy's eyes change colour too - they're a darker shade during the day, but as night falls, they transform into this gorgeous light sparkly turquoise. I've noticed this with other fish as well, they tend to go pale at night and darken during the day, and it's not uncommon for their eyes to be affected by this change.

[FinFan]

That explanation makes sense, thanks. Just wondering, is there a specific reason behind this change?