More about color
I mentioned recently that in the world of computers that color is a bit of a nightmare generally. You can specify absolute physical quantities to color spectra and you can buy Pantone swatches which have color calibrated printed areas for unified color but theres something which you can never calibrate or make any adjustment to and that is the human eye. Members of my family have a very common red-green deficiancy and friends are almost grey tone only. Arcana mentioned recently he is color blind to some extent also. Everyone sees color differently to a greater or lesser degree.
If you can clearly see the two digit number in the image below your not color blind or at least red green deficient but there are many charts to check all sorts of color deficiencies - one is not enough to cover them.
Light as I am sure you all know is a continuous spectrum from deep red to deep violet and yet computer screens display them with just 3 - Red, Green and Blue. It just so happens that you can get the effect of most colors that the eye responds to from using a mix of the three. The word 'most' in there is very important and it is a fact that there are colors that simple red, green and blue will never be able to produce. Also, the specific red, green and blue used by monitors and cameras is even more limited. Basically what a monitor can produce is a subset of all colors. Also, what an individuals eye can see is a subset of all colors from all people. Notably that for people who have had their damaged lens removed and substituted with a prosthetic (clear plastic I suppose) one can allegedly see further into the 'ultra' violet than normal people.
All eyes and all devices (monitors, printers) etc have a color gamut which is the range of colours that they can 'deal' with. If you try to send one color from one device into another device, it might end up being 'out of gamut' for that device. A good example of this is an infra red camera sending that color to the eye. Its in gamut for the specialist camera but not for the eye - it needs a color shift up into the visible.
EDIT -- Link to page of tests:
http://colorvisiontesting.com/ishihara.htm
EDIT2 - It also appears that whilst most humans have eye receptors for red, green and blue and that its well known that many species have a fourth receptor for ultraviolet such that, for example, some insects can see patterns on flowers that we cannot, it transpires that some people (mostly women) have a diminished fourth receptor between the red and green and might be able to see some colors that others cannot !
https://en.wikipedia.org/wiki/Tetrac...arriers_of_CVD
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