I'm pretty sure we have pics of DD like this, I'm going to check now. I've read about this happening before. Is it always the case that something is wrong, or can it be nothing sometimes? Now I need to confirm we have a pic like this.

Btw, your son is stunning.
I think it can be a case of it being nothing, if its not happening all the time. I have one photo of DS like this, one photo in literally thousands. Another photo taken in the same lighting at the same time of someone elses child shows the same thing, so I am inclined to think its the camera & the lighting. Wait there was one photo taken at 3 months old where one eye was "whiter" than the other, but it still has a red tone to it and in the very next photo (the shutter was held down so the photos are literally a second a part) its a normal red-eye.

I think to test, its best to do it in a darker room with them facing away from any light source (I think I remember reading it on the Retinoblastoma website). I assume it opens the pupil up more? I'm a bit on the paranoid side so have done a ton of photos of DS.... and will again tomorrow no doubt :/

OP, sending my thoughts to your gorgeous boy and your family