I know from the art class I took in elementary school that there are primary colors and secondary colors. The primary ones being Red, Orange, Yellow, Green, Blue, and Purple.
So my question is why do we use red, green, and blue? Wouldn’t it make more sense to do every other color on the spectrum so that all colors in between could be mixed from them? Like Red, Yellow, and Blue?
In: Technology
The eye sees color in a spectrum, and there are relationships between the color sensing cells inside the eye. These cells allow the eye to sense a specific color space, the [CIE 1931 space](https://en.wikipedia.org/wiki/CIE_1931_color_space#CIE_xy_chromaticity_diagram_and_the_CIE_xyY_color_space). This chromaticity diagram shows how the relationship between color frequency and the eye’s perception of it. You could use many colors, but due to the shape of the space you can cover most of it with combinations only three colors if those colors are red, green, and blue. You can use other colors of light, and cover other parts of the space, but red, yellow, and blue only covers the lower right half of the space, so it’s not as good as red green and blue.
Because the cone cells in your eye can detect red, green, and blue light, and from the information taken from these color detecting cell’s signals your brain interprets all the other colors you can see.
All colors can already be mixed from red green and blue. Yellow is red + green. Orange is actually also red + green and purple is red + blue.
Red green and blue are already the primary colors. This is true because human eyes are sensitive to wavelengths peaking in three areas: red, green, and blue. Any other colors would add extra information that has alreay been covered.
The “primary” colors are arbitrary and depend on the medium. It’s actually kind of disingenuous to be taught there are objective primary colors, because there aren’t. There’s colors that are useful for a given medium. For blending light, useful colors are Red, Green and Blue because you can mix those three colors to make a very large color space with a relatively simple encoding to represent it.
For ink, often there’s Cyan, for instance because that is more useful when mixing inks.
Color is just reflected light, and mixing colors of different things are going to have different outcomes. For instance, you cannot get the same color space with red, green and blue when mixing paints of different types.
Anyway, the point is to say, there’s really no such thing as primary colors. There’s just color palettes that are useful.
There are two kinds of color mixing. Mixing colored pigments (like paints) and mixing colored lights don’t work the same way. The two systems of color mixing have different primary colors, and you get different results when you mix, say, red and green in the two systems.
If you mix red and green paint, if you have the exact right shades of red and green, you get black. (In practice, you’ll probably get a brown or dark gray color.) Crayons work the same way as paints. The primary colors here are red, yellow, and blue. As you mix more colors, you generally get darker colors.
If you mix red light and green light, you don’t get black or brown. You get yellow. The primary colors here are red, green, and blue. If you mix all three primary colors of light, you get white light. As you mix more colors, you get lighter colors (because you’re adding more light).
Screens use red, green, and blue as primary colors. Printers use red, yellow, and blue.
Latest Answers