# Color triangle physics

## Primary colours and secondary colours

Primary Colors

The colors that cannot be obtained by mixing any other colors in any proportions are called primary colors. The primary colors of light arered, green, and blue.These colors are also called basic colors of light. the reason for considering red, green and blue as primary colors is that all the other colors are made by mixing primary colors in suitable proportions. An interesting thing to be noted about primary colors is that when red, green and blue colors are mixed together they make white light.

Secondary Colors (Composite Colors)

The colors produced by mixing any two primary colors of light are called secondary colors or composite colors.Magenta, cyan and yellow colors are secondary colors.

Experiment for Formation of Secondary Colors

Take three torches and cover there glasses with red, green and blue cellophane papers, so as to produce red, green and blue light respectively. Now, switch on the torches and project all the three coloured lights on a white screen or wall, so that these coloured light may overlap. Now, you will observe that the area where red and green coloured lights overlap appears yellow. And the area where red and blue coloured lights overlap appears magenta. In the same way the area where blue and green coloured lights overlap gives cyan colour. Also, you will observe that the area where all the coloured lights overlap, appears white. We can also write these results as given below:

Red      +      Green      =      Yellow

Red      +      Blue      =      Magenta

Blue      +      Green      =      Cyan

Complementary Colors

Complementary colors are the two colors, which give white light when mixed together.For example, red and cyan are complementary colors because they produce white light on mixing together. In the same way, blue and yellow, and green and magenta are also complementary colors. The complementary colors can be easily remembered with the help of figure given below. The colors present exactly opposite to each other in the triangle are complementary colors.

Colour Triangle to show formation of secondary colors from primary colors

The use of complementary colors is also common in our daily life. The best example of it is the mixing of indigo in lime during white washing of buildings. Actually, with the passage of time the colour of buildings becomes yellowish. Because blue colour is complementary colour of yellow colour so mixing of indigo in lime during white washing keeps the buildings white for a long time.

Pigments

The chemicals which imparts colour to other bodies are called pigments.For example, human blood is red in colour due to the presence of heamoglobin pigment in it. in the same way, the colour of most plants is green due to the presence of chlorophyll pigment.

Sours: https://funscience.in/primary-colours-and-secondary-colours/

## Color triangle

arrangement of colors within a triangle

A color triangle is an arrangement of colors within a triangle, based on the additive combination of three primary colors at its corners.

An additive color space defined by three primary colors has a chromaticitygamut that is a color triangle, when the amounts of the primaries are constrained to be nonnegative.[1][2]

Before the theory of additive color was proposed by Thomas Young and further developed by James Clerk Maxwell and Hermann von Helmholtz, triangles were also used to organize colors, for example around a system of red, yellow, and blue primary colors.[3]

After the development of the CIE system, color triangles were used as chromaticity diagrams, including briefly with the trilinear coordinates representing the chromaticity values.[4] Since the sum of the three chromaticity values has a fixed value, it suffices to depict only two of the three values, using Cartesian co-ordinates. In the modern x,y diagram, the large triangle bounded by the imaginary primaries X, Y, and Z has corners (1,0), (0,1), and (0,0), respectively; color triangles with real primaries are often shown within this space.

### Maxwell's disc

Maxwell was intrigued by James David Forbes's use of color tops. By rapidly spinning the top, Forbes created the illusion of a single color that was a mixture of the primaries:[5]

[The] experiments of Professor J. D. Forbes, which I witnessed in 1849… [established] that blue and yellow do not make green, but a pinkish tint, when neither prevails in the combination…[and the] result of mixing yellow and blue was, I believe, not previously known.

— James Clerk Maxwell, Experiments on colour, as perceived by the eye, with remarks on colour-blindness (1855), Transactions of the Royal Society of Edinburgh

Maxwell took this a step further by using a circular scale around the rim with which to measure the ratios of the primaries, choosing vermilion (V), emerald (EG), and ultramarine (U).[6]

Initially, he compared the color he observed on the spinning top with a paper of different color, in order to find a match. Later, he mounted a pair of papers, snow white (SW) and ivory black (Bk), in an inner circle, thereby creating shades of gray. By adjusting the ratio of primaries, he matched the observed gray of the inner wheel, for example:[7]

To determine the chromaticity of an arbitrary color, he replaced one of the primaries with a sample of the test color and adjusted the ratios until he found a match. For pale chrome (PC) he found . Next, he rearranged the equation to express the test color (PC, in this example) in terms of the primaries.

This would be the precursor to the color matching functions of the CIE 1931 color space, whose chromaticity diagram is shown above.

• Drawing of Maxwell's color top

• A color triangle attributed to Fick in 1892, based on imaginary primaries corresponding to the three primary sensations of the human eye. In such a triangle, all real colors fall within the curved outline defined by the "pure sensations".

### References

Sours: https://en.wikipedia.org/wiki/Color_triangle

## A concept of primary colors [closed]

It's a common conception that there are at least three different colors which produce most of the visible spectrum.

I am wondering if there is a unique set of these "primary" colors which could be chosen as the best one.

For instance, what's the difference between the sets and and if I were to choose a better option, which one would I pick?

Series of comments pointed out that the question is not so clear.

Firstly, let's say that we're calling the human-visible spectrum (which is, more or less, defined (yet, empirically) between certain wavelengths) a .

Now, using terms , , , , etc. I mean the wavelengths (rather, localized wave packets around some wavelengths) commonly associated with these names. The names are not of any importance, really.

Addition of several combinations of localized wave packets (i.e. colors) are possible in different situations.

By I mean the event when a human mind cannot differentiate the superposition of the several wave packets from a single localized wave packet (lying at a, generally, different wavelength in the spectrum).

For instance, the perception of the superposition of $\lambda_1$, $\lambda_2$, $\lambda_3$,... wave packets (with known intensities, of course) can result into the same brain signals which are resulted from a single $\lambda$ wave packet (again, with some intensity).

1. Is this $\lambda$ unique? Meaning that for each human (excluding, maybe the colorblind ones) a predefined set of wavelengths and intensities would result to the same wavelength/intensity of the "mixed" color?

2. If I want to construct the most number of different wavelengths for these "mixed" colors (taking into account that the set is continuous, I'd talk about the greatest measure for the subsets of the visible color spectrum rather than "most number" of colors), a) what is the least number of finite wavelengths which could, by combining them with different intensities, obtain such a result? b) where do these finite wavelengths, most likely, reside in the visible spectrum?

(For instance, if you'd answer 3 colors: RGB, I would like to know why and if they can produce more colors than the RYB or some random choice of 3 different colors.)

$\endgroup$Sours: https://physics.stackexchange.com/questions/267549/a-concept-of-primary-colors
Coheed and Cambria - The Physics of Color Documentary

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## Triangle physics color

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The Physics and Psychology of Colour - with Andrew Hanson

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