How many colors are there?

[ChaosGod]

*Originally posted by JohnClay *
**We can see many colours that aren’t shown on a computer screen though… **

Here is a link to a sketch of the Chromaticity diagram

You can see that the colors Red, Green and Blue are plotted inside forming a triangle. Only the colors within the triangle can be formed combining red green and blue. So as you can see, many colors lie outside of the triangle, and therefore cannot be formed using combinations of R,G & B. This holds true for any combination of three visible colors. Thats the reason computer monitors and TVs can’t show all possible colors the eye can see.

[Ludovic]

I say four. The three colours our color receptors receive and the white that our b+w receptors receive. We interpret all others in terms of these.

In fact, when I am in a park-like natural surrounding, with, for instance, brown bark of tree trunks, green of leaves and grass, blue of sky and water, and white of cloud, I feel most comfortable. In fact, sometimes it seems that something is missing, a lot of the time it is a missing fourth color.

[antechinus]

*Originally posted by Ludovic *
**I say four. The three colours our color receptors receive and the white that our b+w receptors receive. We interpret all others in terms of these.

In fact, when I am in a park-like natural surrounding, with, for instance, brown bark of tree trunks, green of leaves and grass, blue of sky and water, and white of cloud, I feel most comfortable. In fact, sometimes it seems that something is missing, a lot of the time it is a missing fourth color. **

I wonder if it would ever be possible to genetically engineer a gene that expresses new kind of cone that has maximum absorbance at ‘blue-green’ 480nm or at red 650nm.

The brain would learn to cope with the extra signals as it grows from a baby and the colour perception would be much more discriminating than natural colour perception.

[dtilque]

*Originally posted by antechinus *
I wonder if it would ever be possible to genetically engineer a gene that expresses new kind of cone that has maximum absorbance at ‘blue-green’ 480nm or at red 650nm.

The term you want is tetrachromat, and it’s possible there are people (all of them women) that are natural tetrachromats. The reason they are all women is that the genes for red and green photopigments are on the X chromosome. If one of these is slightly different, it will respond to a different wavelength of light. A modification on a man’s X chromosome still leaves him with three photopigments, but a woman could have two different greens or reds.

You can google on the term for more.

[spinky]

Two points:

1. There is more than one way of making a “color”. Take a nice purple, for example. You can have light waves of the frequency which happens to correspond with “purple”, and you can also mix the right amount of blue light with the right amount of red light and get the same color (but not for all colors – as has been pointed out, some can’t be mixed this way). Same color to our eye, but different frequencies. Why do I mention this? Because it destroys the argument that the number of colors is finite due to the quantization of frequencies. You should be able to effectively produce a color halfway between two quanta by mixing equal parts of light of the two frequencies. Mixing at various ratios can give you infinite combinations. Of course, this phenomenon of mixing two colors producing a 3rd color is an artifact of the way our eyes work, so you could argue that the number of colors achievable is either the number of distinct frequencies that can be generated or the number of different colors our eyes can perceive, both of which are finite.

I guess what I’m trying to say is that it depends on how you define the existence of a color. If we had an infinite precision measuring device which used similar technology to our eyeballs (i.e. using a few different types of receptors which each respond to a particular frequency band, as opposed to something which measures the presence of a particular frequency), we could indeed measure an infinite number of unique frequency mixtures (and an awful lot of non-unique ones as well).

2. Just for fun, I thought I’d mention that high-end computer graphics are sometimes done in 48-bit color (16 bits per channel of R,G and B), which comes out to 281474976710656 colors. If I counted my digits right, that’s 281 trillion. Whew!

[FranticMad]

ntucker has it exactly right. “Color” can mean two different things based on either physics or perception.

To illustrate the point consider this:

White light does not exist. There is no single frequency of a photon that is white. There is only a range of colors from dark red (just above infra-red) to violet (just below ultra-violet).

White color is perceived only because our eye and brain combine signals to create the experience of white. White exists nowhere but in your mind.

Furthermore, the concept of “primary colors” is somewhat arbitrary. You could say that sunset orange, bondi blue, and heliotrope are the primary colors, and still mix them so you can perceive the other colors. As long as your choices for primary colors will stimulate a combination of color receptors in the retina in their complete range, then you will perceive all available colors.

[Boldface_Type]

*Originally posted by ntucker *
**Two points:

1. There is more than one way of making a “color”. Take a nice purple, for example. You can have light waves of the frequency which happens to correspond with “purple”, and you can also mix the right amount of blue light with the right amount of red light and get the same color (but not for all colors – as has been pointed out, some can’t be mixed this way). Same color to our eye, but different frequencies. **

This phenomenon is called ‘metamerism’ BTW.

combinations. Of course, this phenomenon of mixing two colors producing a 3rd color is an artifact of the way our eyes work, so you could argue that the number of colors achievable is either the number of distinct frequencies that can be generated or the number of different colors our eyes can perceive, both of which are finite.

I don’t think it’s meaningful to speak of the number of ‘colours’ being equal to the number of distinct frequencies, since there exists any number of colours that look the same but which are composed of different frequencies. Colour arrives through perception, it is not a property of the world per se. For example, an imaginary creature might be able to see radiowaves and thus speak of colour for frequencies outside our visible range.

Franticmad:
White color is perceived only because our eye and brain combine signals to create the experience of white. White exists nowhere but in your mind.

All colours exist nowhere but in the mind!

[coyasicanbe]

*Originally posted by roadkiller *
**I say, if they made it into a crayon, then it’s a color. If it’s not a crayon, then it’s not a color. Like the whole “is clear a color?” thing. You don’t see any clear crayons, now do ya?

When it all boils down, kindergarten logic works for me. **

Thanks roadkiller; I agree. Although the rich kids always said there were 128 colors, my mother told me it just wasn’t true.