Additive vs Subtractive Color: How Mixing Works

Understanding Additive and Subtractive Color Models

Additive and subtractive color models describe how color is formed through either light emission or light absorption. Digital screens create color by emitting red, green, and blue light, while printed materials create color by absorbing portions of white light using inks.

Understanding the distinction between these models is essential when moving work between screen and print, because identical colors cannot exist in both systems without approximation.

Additive Color Mixing (RGB)

The additive color model is based on emitted light. It uses red, green, and blue as primary channels, commonly referred to as RGB. Screens control the brightness of each channel to create color.

Red:   #FF0000 → rgb(255, 0,   0) → hsl(0°,   100%, 50%)
Green: #00FF00 → rgb(0,   255, 0) → hsl(120°, 100%, 50%)
Blue:  #0000FF → rgb(0,   0,   255) → hsl(240°, 100%, 50%)

In additive mixing:

• Adding light increases brightness
• All channels at zero produce black
• All channels at full intensity produce white

Black: rgb(0,   0,   0)
White: rgb(255, 255, 255)

RGB is used by monitors, phones, televisions, LED panels, and any system that emits light.

Subtractive Color Mixing (CMYK)

The subtractive color model works by absorbing wavelengths from white light. It uses cyan, magenta, and yellow as primary inks, with black (K) added for density and contrast. This model is used in printing and physical materials.

Cyan:    #00FFFF → rgb(0,   255, 255)
Magenta: #FF00FF → rgb(255, 0,   255)
Yellow:  #FFFF00 → rgb(255, 255, 0)

In subtractive mixing:

• Adding ink reduces reflected light
• White paper reflects nearly all light
• Layered inks darken the result

In theory, cyan, magenta, and yellow combined absorb all light and produce black. In practice, impurities result in dark brown or gray, which is why black ink is added in CMYK printing.

Key Differences at a Glance

The Inverse Relationship Between RGB and CMYK

RGB and CMYK are mathematically inverse systems. The secondary colors of the additive RGB model are the primary colors of the subtractive CMYK model, and the secondary colors of CMYK align with the RGB primaries.

This occurs because each CMYK primary ink absorbs one RGB primary channel:

• Cyan ink absorbs red light, reflecting green and blue, producing RGB cyan #00FFFF.
• Magenta ink absorbs green light, reflecting red and blue, producing RGB magenta #FF00FF.
• Yellow ink absorbs blue light, reflecting red and green, producing RGB yellow #FFFF00.

RGB mixing adds light to reach white, while CMYK mixing removes light to reach black. The systems produce similar colors through opposite physical processes.

Mixing Direction Comparison

Additive (RGB)

Start: Black
Add Red + Green → Yellow
Add Blue → White

Subtractive (CMYK)

Start: White
Add Cyan + Magenta → Blue
Add Yellow → Black

RGB moves toward brightness. CMYK moves toward darkness.

Practical Use by Medium

• Web and UI design: Use RGB for accurate on-screen color
• Digital illustration: Work in RGB until final output
• Print design: Convert to CMYK and proof carefully
• Brand systems: Define RGB for digital, CMYK or Pantone for print

Common Pitfalls

• Expecting RGB colors to print identically in CMYK
• Using extremely saturated RGB colors outside the CMYK gamut
• Ignoring black ink behavior in CMYK builds
• Failing to proof designs under print conditions

For example, a bright RGB cyan #00FFFF may dull significantly when converted to CMYK because no equivalent ink can emit light.

Applying This in Real Projects

Determine the final medium before choosing a color model. Design in RGB for screens. Prepare and proof in CMYK for print. Expect visual differences when converting between systems.

Tools like Swatching can help extract RGB values from images, explore CMYK approximations, and identify colors likely to translate well between digital and print workflows.