Once when I put some classical red-green 3d pictures on our site I looked up on the Internet if they work for colorblind people. They do, as I expected. But there is more to that. It wasn't this link http://blog.modernmechanix.com/2007/07/20/glasses-let-color-blind-see-red-light/ but a similar one. Not red-green but red-grey or orange-grey glasses help to distinguish red because it looks bright to one eye and dakr to the other, so it gives a flickering effect.

So my question, couldn't people with normal eyesight also build glasses that help us to distinguish shades that look the same to us now? Like short-wavelength violet that is close to ultraviolet and a violet made op of blue and red? Or clean one-wavelength green and a green made of blue and yellow?

We all know there are lots of birds that have white wings.  Recently, many bird species have been proven to be tetrachromatic i.e. they have cone opsins able to absorb at UV wavelengths and so can discriminate ultraviolet light as well.  Does this mean that they cannot see white?

There is a light experiment where a coloured disk with equal red, blue and green sectors is rotated. As the rotational speed increases the coloured sectors coalesce into a white disk, thus demonstrating that white light may be considered to be the sum of three primary colours.

I tried doing this using modern technology - a coloured disk rotating on a computer screen. It didn't work, no matter how fast the disc notionally rotated. I seemed to be getting a slow  stroboscopic effect rather than coalescence. 

Is this caused by a feature of computer screens? 

As the origins of life and the eye are ocean-based, it makes sense that the properties of the human eye ("why we see what we see") were largely evolved to perform specific tasks suitable for water. The fact that we can only observe a limited range of the electromagnetic spectrum—the part that water doesn't filter out—being a good example.

However, is the fact that we perceive water as being "clear" important? Is our optic system calibrated to see clean water as "clear". Obviously there are many things to factor in here: what the eye receives, how the brain perceives colour, even how we sociologically define colours, but water having "no colour" and not causing alarm or distress, for whatever reason would seem to be a good default for the whole thing.

Does anyone have any thoughts on this?

What makes the sky change colour at different angles and directions?

a: Where does the sky get its colours/gradient come from?

b: Why is the sky blue above and red towards the horizon? Why not the other way around?

Thanks!

The colour Blue seems to be a rarity among land animals - mammals especially (we never see a blue cow or a blue dog and so on; only birds and fish display blue)  - is there a reason for this?

How do we know that I see red as you see red, or do we even know this at all? also how do we know the vision of other animals eg, if they see in coulour ect.