The color we perceive an object to be is determined by the wavelengths of light that the object reflects. Different wavelengths of light are interpreted by our eyes and brain as different colors. For example, an object that reflects light mostly in the 400-500 nanometer wavelength range will be perceived as violet or blue, while an object that reflects light mostly in the 600-700 nm range will be seen as red or orange. There are a few key factors that influence what color we see for any given object.
The Light Source
The first major factor is the light source illuminating the object. Sunlight, incandescent bulbs, fluorescent lights, and LEDs all have different distributions of wavelengths. This affects what wavelengths are available to be reflected off an object and detected by our eyes. For example, an object that appears reddish-orange under incandescent lighting may shift towards brown under daylight. The color of light sources can vary depending on their temperature – lower temperature light sources like candles emit more yellow/reddish light, while higher temperature light sources like neon lights emit more blue light.
The Object’s Pigments
The second factor is the pigments present in the object itself. Pigments are chemical compounds that selectively absorb some wavelengths of light while reflecting others. The pattern of wavelengths absorbed vs. reflected determines what color we perceive. For example, chlorophyll in plants absorbs mostly blue and red light, reflecting more green light, which makes plants appear green to us. Carotenoid pigments in carrots absorb blue and green light, leaving mainly orange/red wavelengths to be reflected, giving carrots their distinctive color.
Color Constancy and Surrounding Colors
Our perception of an object’s color is also influenced by the surrounding colors and lighting context through a phenomenon called color constancy. Our brain automatically adjusts and compensates so that colors appear relatively constant under changing conditions. For example, a white piece of paper will still appear white to us whether we view it indoors under yellow incandescent lighting or outdoors under blue daylight. Our brain dynamically recalibrates the perceived color so that whites don’t suddenly appear yellow or blue.
Individual Differences
Finally, there are some individual differences in color vision between people that can affect what color is perceived. About 8% of males have some type of color vision deficiency like red-green color blindness, where they have trouble distinguishing certain shades. This is much less common in females. Additionally, some people may have a condition called tetrachromacy, where their eyes contain four types of color receptors instead of the normal three. This allows tetrachromats to see a greater diversity of colors by detecting more shades of red, green, and blue light.
Examples of How These Factors Combine
Let’s take a look at some real-world examples to see how these different factors combine to create the colors we perceive:
Example 1: Trees
The green color of tree leaves is due to the chlorophyll pigment absorbing red and blue light while reflecting green. But if you view trees under red-tinted light at sunset, the leaves may take on a more reddish or bronze hue. The change in illumination shifts the perceived color.
Example 2: Tomatoes
Ripe tomatoes contain carotenoids like lycopene that absorb blue and green light, leaving mainly red. But unripe green tomatoes have chloroplasts that reflect more green. As tomatoes ripen, chlorophyll breaks down and more lycopene develops, shifting the color from green to red.
Example 3: Hydrangeas
Hydrangea flowers can be either pink or blue depending on the soil pH. In acidic soils, the pigment molecules take on a reddish hue, while in alkaline soils, they shift towards purple/blue. Even though the pigments are the same, the color we see changes based on the molecular structure.
Example 4: Hot coals
As coal burns hotter, it shifts from reddish to orange to yellowish-white as soot and impurities burn off. This follows the principle of color temperature – hotter objects glow with more blue/white light. So the shift from red to white indicates increasing heat.
The Science and Mechanisms Behind Color Perception
Now that we’ve looked at some real-world examples, let’s dive deeper into the underlying science and mechanisms that create the colors we perceive…
Wavelengths of Visible Light
Visible light from the sun or artificial lights consists of a spectrum of different wavelengths ranging from about 400 to 700 nanometers. The longest wavelengths around 700nm are perceived as red, while the shortest wavelengths around 400nm are seen as violet. Green, orange, blue, and other colors fall in between. When all visible wavelengths are combined, we perceive white light.
| Wavelength range | Color |
|---|---|
| 400-450 nm | Violet |
| 450-495 nm | Blue |
| 495-570 nm | Green |
| 570-590 nm | Yellow |
| 590-625 nm | Orange |
| 625-700 nm | Red |
Light Absorption by Pigments
When light hits an object, some wavelengths are absorbed while others are reflected. The specific wavelengths that are reflected determine what color we see. Different chemical pigments absorb light at different characteristic wavelengths. For example:
- Chlorophyll absorbs blue and red light, reflecting green.
- Carotenoids absorb blue and green, reflecting orange/red.
- Anthocyanin absorbs green, reflecting red/purple.
The molecular structure of pigments creates these absorption spectra, based on the specific energy levels electrons can jump between.
Cone Cells and Color Opponency
In our retinas, there are three types of cone cells that detect different wavelength ranges – short (S), medium (M), and long (L). Signals from these cones are processed by visual neurons through a mechanism called color opponency:
- Red vs Green opponency
- Blue vs Yellow opponency
- Black vs White opponency
By comparing the relative activation of cone cells, the brain constructs color sensations. People with red-green color blindness lack one type of cone cell, disrupting color opponency channels.
Color Constancy Mechanisms
To maintain constant color perceptions despite changes in lighting, the visual system uses several types of recalibration mechanisms:
- Chromatic adaptation – The retina adjusts its sensitivity to different wavelengths over time.
- Simultaneous color contrast – Nearby colors influence the perceived color of an object.
- Memory colors – Stored color memories for familiar objects override unusual lighting conditions.
These mechanisms keep the colors of objects relatively stable as lighting varies between indoor, outdoor, and other environments.
Practical Applications and Considerations
Understanding the science behind color perception has many practical applications and considerations:
Interior Design and Decor
Interior designers utilize principles of color theory, contrast, and constancy to create aesthetically pleasing spaces. Factors like wall and light colors strongly influence perceptions.
Fashion and Cosmetics
Clothing, makeup, and accessories use combinations of colors and pigments to achieve desired beauty effects. Warm, cool, neutral, and complementary colors create different impressions.
Food Appearance
The visual appeal of food relies heavily on perceiving fresh, vibrant colors. Restaurants may use colored lighting to enhance foods’ appearance.
Digital Displays
Engineers optimize screens and displays to render colors accurately under different ambient lighting conditions. White balance and color calibration are important.
Vision Disorders
Understanding the mechanisms of color vision aids in diagnosing and treating defects like color blindness or loss of color perception.
Psychology and Culture
The psychological impacts of colors, color symbolism, and variations between cultures inform many fields. Marketers also exploit color psychology.
Conclusion
In summary, the colors we perceive objects to have depends on a complex interplay of factors – the illumination, the object’s pigments, surrounding context, and our visual system. Knowledge of color science empowers us to optimize uses of color for aesthetics, utility, and health. While seeming simple on the surface, the question “what color do you see?” has a fascinatingly intricate set of answers behind our visual experience of the world.
