When it comes to color theory, many people think primarily of pigments. The concept of light in color theory is entirely different, where mixing is additive rather than subtractive. As such, color mixing takes on an entirely different form when it comes to lighting.
Rods and Cones
Human sight relies on visual sensors, or rods and cones, which are located in the retina of the eye. Rods are able to function at extremely low intensity but do not process sharp images or colors. Cones are the opposite: they need a lot of light to work, but can easily process color and sharp images. In the eye, there are three different kinds of cone: red, blue, and green, which correspond to the primary colors of light.
Additive Color: Primaries
The primary colors of light are not the same as in pigment color theory. The process of additive color mixing relies on adding green, blue, and red to create white. In subtractive color mixing, these primaries are yellow, blue, and red, and when combined, they create black.
Here are the basic principles of additive color mixing.
Red + Green = Yellow
Red + Blue = Magenta
Green + Blue = Cyan
The Definition of Additive Color
Why is it called additive color mixing? The basic reason is this: adding red to green creates a new color – yellow – which is lighter in hue than the original two. Subtractive color mixing is about moving toward darkness, while additive color works toward white light.
This means that when a white light is on in a room, or in any other given space, it is actually emitting a combination of red, green, and blue light. Most “white” lights are not actually pure white; they are, rather, slightly off white or tinted yellow. Despite our eyes reading this as normal white light, it really means that the bulb features green and red more prominently than blue, but only very slightly.
Inverting the Method – Absorption
What this all comes down to is the light color you are after. For example, if you want magenta light, you may put a magenta filter in front of a beam of white light. What this means, then, is that you are actually removing, or absorbing, all the other light colors that are not magenta – absorbing the green aspect of the white light.
The secondary colors created by additive color mixing are actually the same colors that are used in most printers. This means that it’s possible to mix backward and create the initial three primary colors of light. As such, you can mix the following:
Yellow + Cyan = Green
Yellow + Magenta = Red
Cyan + Magenta = Blue
Again, this may seem counterintuitive, but you might be surprised to find how well this works.