Color mixing is fundamental to many electrical engineering applications, particularly in display technologies, image processing, and computer vision. Understanding how colors combine helps engineers design better displays, cameras, and image processing algorithms.
Key Concepts
Additive Color Mixing: Combining light sources (RGB)
Subtractive Color Mixing: Combining pigments or filters (CMYK)
Color Models: Mathematical representations of color spaces
Human Vision: How the eye perceives different wavelengths of light
Additive Color Mixing (RGB)
Additive color mixing involves combining light sources. This is the principle behind electronic displays like TVs, monitors, and smartphone screens.
Red
Green
Blue
Primary Additive Colors
Red (≈700 nm): Long wavelength light
Green (≈546 nm): Medium wavelength light
Blue (≈436 nm): Short wavelength light
Additive Color Combinations
Red + Green = Yellow
Red
Green
Yellow
Red + Blue = Magenta
Red
Blue
Magenta
Green + Blue = Cyan
Green
Blue
Cyan
Red + Green + Blue = White
Red
Green
Blue
White
RGB Color Model: Colors represented as (R, G, B) where each component ranges from 0 to 255
Example: White = (255, 255, 255), Black = (0, 0, 0)
Subtractive Color Mixing (CMYK)
Subtractive color mixing involves the absorption of light by pigments or filters. This is used in printing, photography, and painting.
Cyan
Magenta
Yellow
Primary Subtractive Colors
Cyan: Absorbs red, reflects green and blue
Magenta: Absorbs green, reflects red and blue
Yellow: Absorbs blue, reflects red and green
Key (Black): Added in printing to improve contrast and save colored ink
Subtractive Color Combinations
Cyan + Magenta = Blue
Cyan absorbs red, magenta absorbs green → only blue reflected
Cyan + Yellow = Green
Cyan absorbs red, yellow absorbs blue → only green reflected
Magenta + Yellow = Red
Magenta absorbs green, yellow absorbs blue → only red reflected
Cyan + Magenta + Yellow = Black
All primary colors absorbed → no light reflected (theoretically black)
Color Models in Electrical Engineering
RGB Color Space
Used in displays where each pixel consists of red, green, and blue subpixels. The intensity of each subpixel determines the final color.
Color = R·(1,0,0) + G·(0,1,0) + B·(0,0,1)
Where R, G, B ∈ [0,1] or [0,255] in digital systems
CMYK Color Space
Used in color printing. The conversion from RGB to CMYK is necessary for accurate color reproduction.
Conversion Formulas:
K = 1 - max(R, G, B)
C = (1 - R - K) / (1 - K)
M = (1 - G - K) / (1 - K)
Y = (1 - B - K) / (1 - K)
HSV/HSL Color Spaces
These models represent colors in terms more intuitive to humans:
Hue: The type of color (0°-360° on color wheel)
Saturation: Intensity or purity of color (0%-100%)
Value/Lightness: Brightness of color (0%-100%)
Color wheel showing hue variation around the circle
Interactive Color Mixing
Adjust the RGB values to see how they combine to create different colors:
Red: 127
Green: 127
Blue: 127
RGB Values: rgb(127, 127, 127)
Hex Code: #7f7f7f
Applications in Electrical Engineering
Display Technologies
LCD Displays: Use color filters with white backlight
OLED Displays: Self-emissive pixels with precise color control
LED Displays: Use RGB LEDs to create full-color images
Projectors: Combine light from separate color channels
Image Processing
Color Correction: Adjusting color balance in images
Color Space Conversion: Transforming between RGB, YUV, etc.
Computer Vision: Using color information for object detection
Signal Processing
Video Compression: Using color subsampling to reduce data
Color Demosaicing: Reconstructing full-color images from sensor data
Study Questions
Explain why RGB is used for displays while CMYK is used for printing.
Calculate the resulting color when mixing light with intensities: R=200, G=100, B=50.
Describe how an LCD display creates the color yellow using its RGB subpixels.
What is the relationship between additive and subtractive primary colors?
Why is the color black (K) added to the CMY model in printing?
How does the human eye perceive different colors, and how does this relate to color mixing?
Explain the concept of gamut and why different devices have different color gamuts.