As previously explained, the concept of primary colors isn’t as straightforward as it might initially seem. In fact, there isn’t just one definitive set of primary colors; instead, there are multiple, even infinitely many, depending on the context and application. The popular sets we often learn about, like RGB and CMY, are simply the most commonly used for practical and historical reasons.
If you visualize colors like RGB or CMY on a color wheel, rotating all three points by the same arbitrary degree will yield a completely new set of primary colors. The prominence of specific sets, such as RGB and CMYK, in our daily lives is largely attributed to human trichromatic vision. Humans possess three types of cone cells in their eyes (along with rod cells, which are less involved in color perception), making us primarily trichromatic. This biological trait influences how we perceive and categorize colors, leading to the adoption of three hues as primaries in both CMYK and RGB color models.
However, it’s crucial to understand that the selection of primary colors is, to a significant extent, arbitrary. Tradition and practicality play a much larger role than any absolute scientific decree. RGB (Red, Green, Blue) emerged first, primarily because it relates to how light is emitted and perceived, forming the basis for screens and displays. CMY (Cyan, Magenta, Yellow) was developed later as a subtractive complement to RGB, essential for processes like printing where colors are created by absorbing light rather than emitting it.
To understand the relationship between RGB and CMY, consider how they interact with light. RGB is an additive color model, meaning colors are created by adding light together. For instance:
Green + Blue = Cyan
Blue + Red = Magenta
Red + Green = YellowWhite light is the combination of all additive primaries:
White light = Red + Green + BlueCMY operates on the opposite principle, as a subtractive color model. Here, colors are created by subtracting or absorbing certain wavelengths of light from white light. Thinking of CMY in relation to white light and RGB:
White - Red = Green + Blue = Cyan
White - Green = Blue + Red = Magenta
White - Blue = Red + Green = YellowTherefore, you can conceptually interpret CMY as -Red, -Green, and -Blue, representing the colors that subtract red, green, and blue from white light, respectively.
The study of color science and the psychology of color perception are incredibly rich and complex fields. It’s particularly interesting to differentiate between perceived color spaces and scientifically constructed color models. Before modern scientific color theory took hold, the most commonly accepted primary colors were Red, Yellow, and Blue (RYB), and Violet, Orange, Green (VOG). Even today, RYB is often considered the “3 psychological primaries,” or RYBG (Red, Yellow, Blue, Green) as the “4 psychological primaries,” despite not being equidistant on perceptually uniform color wheels.
Furthermore, even scientifically constructed color models like RGB/CMYK are limited by the nature of human color perception. They don’t necessarily reflect an objective reality of color beyond how humans see it. Imagine a person born with tetrachromacy – possessing four types of cone receptors instead of three. For such an individual, the colors produced by an RGB television set would likely appear vastly different from the “natural” colors of objects as perceived by trichromatic humans. This highlights that what we consider “primary colors” are deeply intertwined with our biology and the tools we’ve created based on our perception.
