Color Forums

Galley wrote:

Why is it, that in art class you learn that the three primary colors are red, yellow and blue, and in science, the three primary colors are red, green and blue.  After all, green is a mixture of yellow and blue.  :confused:

Probably has to do with the fact that the human eye sees in R,G,B.

I'll try to answer your question without getting too technical

In painting, the primaries are Red, Yellow and Blue because you can create any color in the spectrum simply by mixing a combination of these colors.  After all, this is the definition of a "primary".  Want orange?  Mix equal parts red and yellow.  Need purple?  Mix red and blue.

Digital (or screen) colors don't work this way though.  The color of each pixel on your computer monitor, TV, or any other digital device is made up of varying percentages of Red, Green and Blue.  So to get orange you would need 100% red, 50% green and 0% blue.  This has to do with the fact that light is being emitted from the object you are looking at, rather than light reflecting off of it.

Take a look at this link for a nice in-depth explanation posted by someone on Google Groups:
http://groups.google.com/groups?hl=en&a … or%2Bspace

I hope that helps clear up some of your confusion.  It's definitely a tricky subject!

When you went to school you learnt that the three primary colors are red, yellow and blue, and now that you are involved with the web, the three primary colors are red, green and blue.
Our monitors (CRT) Cathode Ray Tube. Have at their rear 3 electron emitters (guns)red, green, blue, each beam is slightly different, the electrons strike the phosphors on the inside of the screen, the phosphors glow one of three colors. Your TV has the same setup. The result is a projected/transmitted light beam. Think of a rear projection TV, and think about 3D glasses.
The color (light) is made by adding differing amounts of other colors from the  primaries (RGB)? RGB light beams are being projected/transmitted at varying amounts, pure white is R=255 G=255 B=255 at maximum addition they have each cancelled out the others, as the RGB values drop so we get our colors appearing.
Think of a stained glass window, it does not reflect light, its color is transmitted.
Monitors and TV’s are our artificial means attempting to copy nature, we have learnt that our tools to do this have shortcomings, we juggle, bend and twist our tools to get close to nature, its not perfect, but its not bad, in fact its pretty damn good considering! Now, LCD screens are a different animal, and I will leave it there.

The confusion with viewing a painted, printed or natural surface is that we are looking at reflected light. In printing or painting, we start with the subtractive primaries (CYM) (cyan, yellow, magenta) and mix those in varying amounts (plus BLACK abbreviated as K) to get the colors we see printed in magazines and books.
Colors are mixed proportionally in percentages such as:
50% CYAN 100% YELLOW 25% MAGENTA 
This CMY(K) color model is only one of many ways we can express color for print — but we'll save that topic for another feature.
There are other color-related terms and models, different terms work together and interact to describe the colors we see in the world, in print, and on the Web.
Did you know that the color wheel you learned in school isn't the same as the colors used for the Web? It's not even the way colors are mixed for printing? Well, ok, same colors, just different arrangements and mixes.
• The traditional primary colors are RED, YELLOW, and BLUE.
• Mix two primary colors to get the complementary colors.
• The traditional complementary colors are ORANGE (Red plus Yellow), GREEN (Yellow plus Blue), and PURPLE (Blue plus Red).
In grade school you probably had plenty of opportunities to mix primary colors and make new colors. It was magic!
 
The way we see color is a bit different. You've probably seen a prism break a beam of light into a rainbow of colors. The visible spectrum of light breaks down into three color regions: RED, GREEN, and BLUE.
• Add RED, GREEN, and BLUE (RGB) light to create WHITE light. Because you ADD the colors together to get White, we call these the additive primaries.
• Subtract one of the colors from the other three and you are left with yet another color. RGB minus RED leaves CYAN. RGB minus the BLUE leaves YELLOW. RGB minus GREEN leaves MAGENTA. These are called the subtractive primaries (CMY).
Try mixing GREEN and BLUE paint and I bet you don't end up with a nice CYAN. Why? Because the color we see is reflected light and light and ink don't work in quite the same way.
 
Now put all this aside for a bit and look at the way we try to reproduce color in print and on the Web.