Color is a fundamental part of human perception and experience. We see color everywhere around us – in nature, man-made objects, digital displays, and more. But where does color come from? How is it created and perceived by our eyes and brain? Understanding color theory and the basics of how color works can help us utilize color more effectively in design, art, photography, and other visual media. This article will provide a brief overview of the physics of color, as well as explain the concepts of additive and subtractive color systems.
The Physics of Color
In simple terms, color is light. What we perceive as color is electromagnetic radiation from the visible spectrum striking the retina of the eye. The visible spectrum is the portion of the full electromagnetic spectrum that is visible to the human eye – ranging in wavelength from about 380 to 740 nanometers (nm).
The wavelengths of light from the visible spectrum can be represented as colors – the longest wavelengths appear red, transitioning through orange, yellow, green, blue, indigo, and finally violet at the shortest wavelengths. When all wavelengths of the visible spectrum are present with roughly equal intensity, we perceive this as white light. The absence of light we perceive as black.
Different surfaces and materials absorb and reflect different wavelengths of light. The wavelengths that are reflected determine what color our eyes see. For example, a banana appears yellow because it absorbs blue and red wavelengths, while reflecting back yellow wavelengths more.
Additive Color Systems
Additive color systems involve light emitted directly from different light sources. The primary additive colors are red, green, and blue (RGB). Combining red, green, and blue light in different proportions can create all the colors of the visible spectrum.
Additive color systems use transmitted light sources like television and computer monitors, projectors, and other digital displays. Pixels on these displays contain tiny red, green, and blue LEDs (light emitting diodes). Varying the intensity of each LED allows millions of possible color combinations.
By mixing red, green, and blue light we get the following additive secondary colors:
| Red | + | Green | = | Yellow |
| Green | + | Blue | = | Cyan |
| Blue | + | Red | = | Magenta |
Combining all three primary colors of light at full intensity results in white light:
| Red | + | Green | + | Blue | = | White |
The absence of all three primary colors of light results in black.
Subtractive Color Systems
Subtractive color systems involve reflected light and depend on transmission, absorption, and reflection of wavelengths by different pigments. The primary subtractive colors are cyan, magenta, and yellow (CMY). These are the opposite, or complementary, colors to the additive RGB primary colors.
In subtractive systems, all wavelengths are initially present in white light. Color is created by subtracting (absorbing) certain wavelengths and selectively reflecting back the remaining wavelengths. For example, magenta pigment absorbs green wavelengths and reflects back red and blue. Cyan absorbs red and reflects blue and green.
The secondary subtractive colors are created by combining two primary subtractive colors:
| Cyan | + | Magenta | = | Blue |
| Cyan | + | Yellow | = | Green |
| Magenta | + | Yellow | = | Red |
Combining all three primary subtractive colors absorbs all wavelengths, resulting in black:
| Cyan | + | Magenta | + | Yellow | = | Black |
The absence of all subtractive primaries reflects back all wavelengths, creating white.
Common examples of subtractive color mixing are painting and inks. Paints contain pigments that selectively absorb and reflect different wavelengths of light. Overlapping painted areas mixes the reflected colors to create new hues. CMYK printing uses cyan, magenta, yellow, and black inks on white paper to produce color images.
Key Differences Between Additive and Subtractive Systems
While both additive and subtractive color systems aim to recreate the colors of the visible spectrum, there are some key differences between the two:
| Additive (RGB) | Subtractive (CMY/CMYK) | |
| Uses transmitted light | Uses reflected light | |
| Red, green, blue primaries | Cyan, magenta, yellow primaries | |
| Combines colors by adding light | Combines colors by subtracting wavelengths | |
| White results from combination of all colors | Black results from combination of all colors | |
| Computer/TV displays, projectors | Paints, inks, pigments |
Additive mixing starts with darkness and adds light wavelengths together to form colors. Subtractive mixing starts with white light and selectively subtracts wavelengths to create colors.
Color Perception
The cones in our retina contain photopigments that are sensitive to red, green, and blue wavelengths. Signals from these cones are processed by the brain to give us our perception of different colors. While additive RGB and subtractive CMY are complements, they do not perfectly match the way we sense color biologically.
Other factors also influence color perception, including surrounding colors, lightness/darkness, saturation, memory colors, culture, and more. Ultimately color is a complex neuro-biological process as much as a product of physics.
Other Color Systems
While RGB and CMY(K) are the most widely used color models, there are other color systems and models that serve different purposes:
– RYB (red, yellow, blue) – Historical artists’ color wheel, still used in painting today. The primary colors differ from modern understanding of color, but provide some practical benefits for mixing paints.
– Pantone Matching System – Proprietary color reproduction system that provides designers and printers with swatches of precise, pre-mixed ink colors for graphic design.
– HSB/HSV (hue, saturation, brightness/value) – Represents colors in terms of hue angle (0-360°), percent saturation, and brightness. Useful for adjusting colors in digital design and editing software.
– CIELAB/CIEXYZ – Color models based on measurable human perception metrics, useful for comparing/quantifying differences between colors. Used for color management across different devices.
– NCS (Natural Color System) – Models color psychologically in terms of similarities to common “reference” colors. Designed for practical color communication and specification.
Conclusion
Understanding the basics of additive and subtractive color theory allows us to utilize color more intentionally and effectively. While modern color systems aim to faithfully reproduce the spectrum of visible colors, our perception of color is complex, subjective, and influenced by physiology, psychology, culture, and context. Color technology continues advancing, but the magic and artistry of color remain eternally linked to our human experience.