Good on ya, Noelm. You investigated for yourself.
but it seems somehow obvious that their eyes are way different to ours.
That is exactly right, Noel. Few fish have similar eyesight to humans. So they see things differently.
From research, we know that barramundi eyes are pretty much the same as ours (except for the "party trick" tapetum lucidum - low light party trick). So we can relate to what barramundi see.
If however a red emperor has different eye characteristics to humans (say that they can't see green), then we have to use a suitable colour filter on our eyes to block out green to see like a red emperor. I used different coloured cellophane to make the filters to let me see what "the steelhead man" was talking about.
THEN we know what THEY see.
Do you want to see what Colin Kageyama says about the stuff you are talking about? He researched it pretty well.
You can buy the book. I obtained it and it was a real eye opener (so to speak).
What Fish See by Colin J. Kageyama (bradwiegmann.com)
Colin K is a US steelhead fisherman and his research relates to that species because he knows eyesight detail about steelheads.
I did barramundi for similar reasons.
I can scan some of the pages that you might interesting if you like. Might help you to understand what really happens underwater with colours (not just the myth and b/s that abounds) and maybe assist you if you want to buy it yourself.