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Is every color in the rainbow

October 11, 2011

Yesterday, I asked the question, “Is every color in the rainbow?“:

Here are some places our discussion went:

Yes, the rainbow has all the colors.

No, there are obvious examples of colors not in the rainbow: brown, black, gray, periwinkle, etc..

The rainbow provides the “toolbox” to make all the colors, but it doesn’t have all the colors. Colors like brown, pink, white are not in the rainbow, but could be made by mixing rainbow colors. This leads to question, how many tools are in the toolbox

Idea #1: Some believe that the only true colors in the rainbow are  ROYGB(I)V, with colors like red-orange being blends of red and orange. ROYGBV are seen as the basic colors that you make all the other colors with. Most with this idea agree that red-violet is not possible in the rainbow because they dont’ overlap.

Idea #2 Others thought that the only true colors in the rainbow are RYB, with colors like orange being simple blends of red and yellow. It is generally recognized that purple is an issue with this idea. There are some very exciting ideas about how purple might be ending up in the rainbow, including that rainbows aren’t 2D but are twisted around themselves like a tube so that R&B do overlap to make purple. Another idea is that purple shows up because rainbows are often double rainbows, so that the stacked nature of rainbows allows purple arises when the bottom of one overlaps with the top of another rainbow. I like how topological these ideas are.

Idea#3: There are an uncountable numbers of colors in the rainbow. We tend to only name a few colors we are familiar with, but we could point anywhere on the rainbow a see a new color, which we could name whatever we want. Our class has been using the name “Walch” as the example new name for a color.

Metallic named colors such as copper, bronze, gold, silver, chrome are not in the rainbow. There is the idea that gold just means “shiny” yellow and that silver means “shiny gray”.

Some colors leave people uncertain about. Pink, for example, might be in the rainbow, because we could consider it a shade of red, and red is in the rainbow. White might be in the rainbow, since some people believe that adding all light colors together makes white. Many state that it depends on what we mean by “color”, and others think it depends upon what we mean by “in” the rainbow.

The definition of color is certainly an issue. One proposed definition of color is this: “We know it when we see it”. Another definition was more like  this: “Any place on the rainbow you can point to and give a name is a color” Another is, “ROYGBIV define the true colors”… or “RYB define the true colors.”

In human pigment, white (or albino) is a lack of color. Thus white is a lack of color. On the other hand, projectors work by shining three colored lights, and those lights combined make white light. On the other hand, mixing a bunch of paint colors together gets your black or brown.

Prisms make rainbows by spreading light out into different colors. What happens when you collapse a rainbow back down? Does it turn white? Turn colorless? Do the rainbow colors change because they overlap more?

Other Questions that arose:

Why isn’t violet in between red and blue on the rainbow? It would be on the color wheel.

Is sunlight “white” or is it “colorless”?

When you mix all the colors, do you get white, black, or brown?

Are black and white colors?

What do we mean by tints, shades, hues?

How do rainbows work?

How do projectors, printers, computers, and paint work differently/similarly?

What causes color-blindness?

Are there colors that exist in the world that we’ve never experience before?

Why does light color seem to have different rules than pigment (paint color)?

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3 Comments leave one →
  1. Christopher permalink
    October 13, 2011 1:28 am

    This is a fabulous question.

  2. October 18, 2011 1:54 am

    Hi Brian, food for thought from XKCD.

    Randal Munroe polled his readers on their color perceptions http://aram.xkcd.com/color/

    He got some really interesting information out of the survey about how people perceive color in RGB space. http://blog.xkcd.com/2010/05/03/color-survey-results/

  3. Sommie permalink
    March 1, 2015 12:04 pm

    So, what’s the answer?

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