Why is the concept of red, yellow, and blue being the sole primary colors not universally appropriate?

Question

Why is the concept of red, yellow, and blue being the sole primary colors not universally appropriate? When would you use this system, and when would you use others?

Answer 1

This works with mixing pigments, for example, but not with light or ink. Television and inkjet printers, among others, use a different system.

Answer 2

The term used in graphics, and in physics is "gamut," which, roughly, means the range of colors and how they are created and percieved.

The red, yellow and blue, as primary colors work, only when mixing, or "additive" colors. With these three pigments, one can mix them to create the secondary colors of green, orange and purple. Adding white and black can produce tints and other, more subtle blends can create many more colors but not ALL visible colors. For example, you can't add black to make a darker yellow. You cant blend equal mixes of these three to make white. (which you may have learned is the mix of ALL colors. Different gamut. More on this, in a moment)

Even commercial and desktop printers use an "additive" color gamut to produce colors in print, but these "primary" colors are slightly different because they mix in a very different way. Printers, mostly use a CMYK gamut, which means the primary colors are cyan, magenta, yellow and black. Rather than the inks being, actually, mixed, tiny dots of pure color are place on white paper, each color being placed next to, but not actually touching an adjacent color. The observer's eye will "mix" the colors in the brain, so that a series of cyan dots, printed among a series of yellow dots will appear to the brain as green. Lighter shades are produce by printing fewer dots, allowing more white paper to show, while darker tints are acheived by putting dots closer together and adding black dots. A greater gamut, or range of colors is done by adding some other colors besides the CMYK ones. They do this, because CMYK does not create all the visible colors. Some greens and blues, for instance, cannot be acheived in print without the addition of these additional colors.

Even then, not every color, visible to the eyes can be made this way.

Computer monitors and televisions use another gamut, known as RGB, after the primary colors of red, green and blue. The human eye "sees" in the RGB gamut. (slightly different than the computer RGB, but VERY close) RGB is a "subtractive" gamut, where other colors are acheived by REMOVING elements of RGB. In fact, pure white is by the equal presence of all three. Which is what teachers mean when they say that white is a mix of ALL colors.

There are other, less known color gamuts, but these are the ones most artists and designers use.

I know this explanation was a little "wordy," but yours is a very good question, deserving a complete answer.

Answer 3

When mixing colors that will blend "normally" with each other, red blue and yellow are the basic three colors (not counting black and white) that every other color can be made from.
But, with certain types of ink or other various things, the blending of the colors just doesn't work the same, somehow. I don't really understand why.

Also, in some cultures they have a set of colors that they call "primary colors" that aren't red, blue and yellow. In such cases, their primary color set is an invented cultural thing where someone thousands of year ago decided that a certain set of colors is the "best" and should always be used in a certain way. Such sets of primary colors aren't based on the actual mixing of colors. When red, blue and yellow are called primary, it's because you can take red, blue and yellow paint and mix them together in different combinations to make EVERY other color imaginable.

Answer 4

Appropriate? it's the law of PHYSICS. The mechanism of the human eye assesses colors according to the refraction of light. Red, yellow and blue were not chosen arbitrarily...they are primary because you cannot make them by mixing any other colors, and all other colors are derived by mixing them. The rods and cones in your eyes allow you to see colors, which is why animals whose eyes are made differently do not receive color.
In photography, the primary colors of light are yellow, magenta and cyan. If you shine a light through filters of all three colors, you get gray.