Basic Color Knowledge
Definition of Color
Color is the result of how our visual system perceives different wavelengths of light. It is a complex phenomenon that integrates physics, physiology, and psychology. Simply put, color is not an inherent property of an object; instead, it is the product of the interaction between light, objects, and our eyes and brain.
We can understand color from the following perspectives:
1. Physical Perspective: The Nature of Light
Light is an electromagnetic wave. Visible light occupies only a very narrow portion of the electromagnetic spectrum (with wavelengths from approximately 380 nm to 780 nm).
Different wavelengths correspond to different colors. For example, long wavelengths are perceived as red, while short wavelengths are perceived as blue or violet.
Sunlight (white light) contains all visible wavelengths. When white light shines on an object, the object absorbs certain wavelengths and reflects or transmits others. The color we see is the portion of light that is reflected or transmitted by the object.
For example, the peel of a banana absorbs most blue and violet light, reflects yellow and red light, so we perceive it as yellow.
2. Physiological Perspective: Processing by the Eyes and Brain
Eyes as receivers:
The retina contains two types of photoreceptor cells—rods and cones.
Cones are responsible for vision and color perception in bright environments. Humans typically have three types of cones, which are most sensitive to long (red), medium (green), and short (blue) wavelengths of light.
Brain as processor:
The three types of cones send signals of different intensities depending on the received wavelength. These signals are transmitted to the visual cortex, where the brain compares, integrates, and interprets them, forming the rich colors we perceive.
This is the basis of the three-primary-color principle: all colors of light can be created by mixing red, green, and blue (RGB) in various proportions (additive color mixing, used for screens and light).
3. Psychological & Cultural Perspective: Subjective Perception
Color perception is subjective and influenced by lighting conditions, surrounding colors, and individual differences (such as color blindness).
The famous “blue-black or white-gold dress” debate is a typical example.
Colors also have strong psychological effects:
Red: passion, danger, excitement
Blue: calmness, trust, sadness
Green: nature, safety, vitality
Different cultures assign different symbolic meanings to colors.
For example, white symbolizes purity in Western cultures, but is associated with mourning in some Eastern cultures.
Key Concepts
Hue: the basic name of a color (red, yellow, blue, etc.).
Saturation: the purity or intensity of a color; high saturation means vivid color, low saturation approaches gray.
Brightness (Value): the lightness or darkness of a color.
Summary
Color is:
A physical phenomenon: determined by light wavelengths
A physiological response: processed by cone cells and the brain
A subjective experience: influenced by psychology, culture, and environment
It bridges objective reality (light) and subjective perception (our neural interpretation).
Definition of Light
Light (visible light) is a type of electromagnetic wave.
The wavelength of visible electromagnetic waves ranges from 380 nm to 780 nm
(1 nanometer = one-billionth of a meter).
Electromagnetic waves outside the visible range are invisible to the human eye:
Shorter wavelengths: ultraviolet and X-rays
Longer wavelengths: infrared and radio waves
Distribution of Light
White light (such as sunlight) contains electromagnetic waves with wavelengths from 380 nm to 780 nm.
When arranged by wavelength:
Fromshort to long: violet → blue → cyan → green → yellow → orange → red
Fromlong to short: red → orange → yellow → green → cyan → blue → violet
Light with only a single wavelength is called monochromatic light.
Monochromatic light arranged in order of wavelength forms an aspectrum.
Approximate wavelength ranges:
Red: 600 nm–700 nm
Green: 500 nm–600 nm
Blue: 400 nm–500 nm
Monochromatic Light
Monochromatic light refers to electromagnetic waves of a single wavelength.
When white light is separated, it splits into multiple monochromatic lights.
When multiple monochromatic lights are combined, they form white light again.
Differences in wavelength, energy, and refractive index of monochromatic light determine the differences in color.
Additive Color Model (RGB)
RGB Primary Colors
Subtractive Color Model (CMY/CMYK)
CMYK Four Base Colors
Color Compensation (Complementary Colors)
Color compensation is also known as complementary color.
Complementary colors lie opposite each other on the color wheel.
When two complementary colors are mixed:
White is produced underadditive mixing (light)
Black is produced undersubtractive mixing (pigment/ink)
RGB and CMY are complementary systems because each color pair has the following relationships:
(Color wheel illustration implied)
Relationship Between Objects and Light
When light shines on an object, the object absorbs the wavelengths complementary to its color and reflects the rest.
Reflection Property of Color Pigments
Cyan pigment absorbsred light; blue and green pass through and are reflected by white paper → perceived as cyan.
Magenta pigment and yellow pigment behave similarly.
Transmission
A transmissive object absorbs part of the white light and allows part of the light to pass through.
Reflection
A reflective object absorbs part of the white light and reflects the remaining part into the eye.
