Color Definition and 34 Discussions

Color (North American English), or colour (Commonwealth English), is the characteristic of visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of photoreceptor cells (in particular cone cells in the human eye and other vertebrate eyes) by electromagnetic radiation (in the visible spectrum in the case of humans). Color categories and physical specifications of color are associated with objects through the wavelengths of the light that is reflected from them and their intensities. This reflection is governed by the object's physical properties such as light absorption, emission spectra, etc.
By defining a color space, colors can be identified numerically by coordinates, which in 1931 were also named in global agreement with internationally agreed color names like mentioned above (red, orange, etc.) by the International Commission on Illumination. The RGB color space for instance is a color space corresponding to human trichromacy and to the three cone cell types that respond to three bands of light: long wavelengths, peaking near 564–580 nm (red); medium-wavelength, peaking near 534–545 nm (green); and short-wavelength light, near 420–440 nm (blue). There may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a color's colorfulness).
The photo-receptivity of the "eyes" of other species also varies considerably from that of humans and so results in correspondingly different color perceptions that cannot readily be compared to one another. Honey bees and bumblebees have trichromatic color vision sensitive to ultraviolet but insensitive to red. Papilio butterflies possess six types of photoreceptors and may have pentachromatic vision. The most complex color vision system in the animal kingdom has been found in stomatopods (such as the mantis shrimp) with up to 12 spectral receptor types thought to work as multiple dichromatic units.The science of color is sometimes called chromatics, colorimetry, or simply color science. It includes the study of the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range (that is, what is commonly referred to simply as light).

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  1. Kyran

    B Why are things the color they are?

    I have not noticed anything in common between all things that are the same color. It must be something on the atomic level but if I look at the periodic table I see no pattern in how things behave and what their color is. So how can the sun be the same color as a highlighter and plastic the same...
  2. W

    I How electrons absorb or emit photons

    Hi, I am aware that the reason why objects have color is an old subject. However I come across two claims which sound like they are in contrast to each other. On one hand I read that the photons with specific frequency in incoming light are absorbed (i.e. have enough energy to move an electron...
  3. Ryan Walsh

    Question about metallic ions and a molecule

    Cobalt(II) Copper(II) Copper(II) tetrachloro complex Chromate Vanadyl(V) (pervanadyl) Dichromate Can these metallic ions make up a certain molecule?
  4. prashantakerkar

    Smartphone torch light

    Is it feasible to design and develop a Smartphone torch app which can display light in different colors selected by the end user? Thanks & Regards, Prashant S Akerkar
  5. R

    Composition of Light

    Hi everyone, I have a few questions about the composition of light: First, what is it? Is white light the result of all color wavelengths present in an area? Second, if so, then why is there no interference in waves of light (or is there)? Third, if photons all travel at the same speed, then...
  6. X

    Does anyone know how to measure the color of a Post-It note?

    I'm not sure if this is the right place for this, but since I'm new here i'll post it here until someone tells me it should go somewhere else. Anyway, I am currently wondering how to measure the color of some post it notes. It started as a friendly argument as to which post it pad was more red...
  7. Const@ntine

    Barrier of Diffraction: Different Wavelengths, Same Color?

    Hey there! We started Lab III last week, but things are a bit... strange. See, those exercises were written back in the early 1900s,and so they ask us to read from a book that was published around 1890 or so. Naturally, the library has only one copy, and it's open for 2hours per week, so it's...
  8. kelvin490

    MATLAB Matlab -- how to make a smooth contour plot?

    I want to represent data with 2 variables in 2D format. The value is represented by color and the 2 variables as the 2 axis. I am using the contourf function to plot my data: load('data.mat') cMap=jet(256); F2=figure(1); [c,h]=contourf(xrow,ycol,BDmatrix); set(h, 'edgecolor','none'); Both xrow...
  9. P

    I Color Theory Equations

    Hey guys I figured out something new about color theory in additive color mixing. So, the primary colors in additive color mixing are R, G, and B (Red, Green, and Blue). The secondary colors are C, M, Y (Cyan, Magenta, Yellow). Using basic knowledge we know that R + G = Y R + B = M G + B = C...
  10. L

    Color of Fe(II) complexes

    There is something that I am not understanding about the visible colors of coordination complexes. I did a lab where I prepared [Fe(NH2trz)3]Br2 from FeBr2. Fe(NH2trz)3 was a violet color and FeBr2 was red. My understanding of colors in coordination complexes is that reds are high energy...
  11. E

    Difference in hues between eyes

    Recently I have become curious of a difference between then colors I see with my left and right eye. After reading a bit about people with a similar experience I have found a pattern, almost every story I have read it seems that the right eye sees deeper colors such as red better and the left...
  12. Eric Putney

    I Can a (uuu) baryon exist? If so, why wouldn't protons decay

    Is this some sort of issue with color or another quantity that needs to be conserved?
  13. kelvin490

    MATLAB How to make 2D plot of points with different colors?

    I want to make a 2D plot of points with different x, y coordinates and have colors depending on a separate variable. I have make column vectors for x and y coordinates and another column containing 1 or -1. I would like to represent the points with 1 as red and -1 as blue points. I have codes as...
  14. J

    LED light wavelengths

    I work in a factory where we package pharmaceuticals. There are quiet a few products that are light sensitive to a certain wavelength. The lights in the older buildings are fluorescent and were have defined wavelength specification. The wavelength determined the color light/filters set in the...
  15. J

    B Color of main sequence stars

    If all main sequence stars are engaged only in hydrogen fusion, why don't they all exhibit the same color?
  16. Remixex

    Basic question about Scattering and understanding colors

    So I'm studying scattering and size parameters now, I've come to understand that the sky is blue because the size parameter is such that it's an excellent "scatterer" of blue-violet visible light, and horrible at red-orange, that let's pass, and such the sun is yellow within the Earth. I've also...
  17. C

    B Are colors in astro photos 'real'?

    There are lots of amazing photographs of nebula around. The colors contribute greatly to their grandeur. But if we were able to get near enough to a nebula to see it with the naked eye would it possesses the colors we see in published photographs taken by telescopes? Or are the colors in astro...
  18. A

    How are the color of an compound and it's constituent elements related?

    Suppose the color of some elements is red and blue but after the reaction between them a new compound formed with yellow color .so on what factor does the the color of compound depend? I think it may depend depend upon the number of electron transferred and the remaining one...
  19. kelvin490

    MATLAB How to set zero value boxes transparent in 3D plots?

    I used a function called ind2patch to make a big 3D block which contains a number of smaller blocks in 3 dimensions. Each small block has a value which the magnitude is represented by a color.One example is shown below: However, most of the boxes have very low or zero value and I don't need to...
  20. baxishta

    B Gluon Color Question

    if "color" is one of the eigenvalues, how may a single gluon be in possession of 2 of them and still be unique? also, a 2-color gluon is reminiscent of a 2-color tao, no?
  21. kelvin490

    MATLAB How to use a suitable color bar?

    I have a picture which shows the magnitude of some value in terms of color, like this one: The higher the magnitude, the more it looks red. However there are only a few points at the edge has very high values and most of the points have...
  22. Anand Sivaram

    Perceived Color of objects: in White light from a TV

    Background: Normal white Sun light has a continuous spectrum in the whole of visible range. But, white light (rather what we perceive as white) coming out of a Monitor/TV is have only RGB in it and it looks white because of the Tricolor vision which excites all three types of cells in the eye...
  23. L

    How does light change color?

    I understand the basics of how vision works, but correct me if I'm wrong at any point. Electromagnetic radiation is emitted from the sun as a byproduct of fusion, in the form of photons. These photons travel a vast distance at an incomprehensible speed, and bounce around the atmosphere a bit. A...
  24. H

    Color of light

    if a ray of monochromatic light comes from a denser medium to a rarer medium does the color reaching a viewer in the rarer medium differ from the actual color of light in the denser medium (as wavelength of light is different for both the media)?
  25. SlowThinker

    Color of light in the Light Clock

    In another thread, I came across the question of how the photon's energy and momentum appears in the moving frame. The question is best explained with the standard light clock. Lets have 2 horizontal mirrors, that is, one above the other. In the rest frame, the photon is set up to be linearly...
  26. Sterling Lutes

    Amount of single photons to make white light?

    First off I hope I'm putting this in the correct forum. My question is more than just the minimum amount of photons to make a single blip of white light, but more so the base photons in the visible spectrum of light. We have all seen a prism split light into violet, blue, cyan, green, yellow...
  27. A

    Can some bright spark help me? Colour of Light vs Time

    I'm writing a Science Fiction story which has one place where time runs at normal speed, and another place next to it, where time runs at a much slower speed. If you stand in the normal place and look into the slow place, you will see people moving around as if in slow motion. But what would...
  28. BiGyElLoWhAt

    On a scale of 1 to String, how speculative is this? Is this a legitimite thing? I've never heard of 4th color charge or quark-lepton unification.
  29. A

    Hydrogen/Helium Emission Spectra Temperature Dependence

    Hi all, Does anyone know where I can find data details of how Emission Spectra depends on temperature for the following materials: Single Hydrogen Molecular Hydrogen (H2) Helium That is, as I heat up each of the above materials by themselves, from room temperature to thousands of degrees, I'd...
  30. A

    Candela and Heat

    hello there, i hope you can help me.. i have a halogen lamp 12V 50watt, in this lamp datasheet, i read there is 1200 cd (MAX). is there any way to know how much the heat that lamp produces? without i testing using thermometer ..
  31. A

    Using Red Light to Reduce Effect of Ambient Light

    Hello, I have heard many times that red lighting is good for imaging applications where the effect of ambient light needs to be reduced to a minimum. What is the theory behind this? Why does red light (vs. other colors) reduce the effect of ambient light? Thank you.
  32. J

    The Law of Reflection and Lasers

    So I've been looking into the Law of Reflection with Specular and Diffuse Reflection. I understand that electrons have a certain vibrational frequency in objects, and if a light wave matches that, that color wouldn't be observed. My question is, what if I took a red laser pointer and shined it...
  33. U

    Quick question on Baryon spin states

    Things I don't understand: What do they mean by "two spin-1/2 doublets and a spin-3/2 quadruplet"? Why do they use the two flavours "+2/3e and -1/3e" ?
  34. J

    Light photons, color and energies of molecules.

    Hi, so I'm a first year neuroscience student at Carelton University in Canada. I had a little bit of a "revelation" with this topic recently after I understood it a bit better and I think this is really interesting. (If I understand it correctly!) We're learning about Kekule structures...