Context

This article sheds light on colour and its significance in understanding how living beings perceive the world.

• Red, green and blue are primary colors.
• Yellow, magenta and cyan are secondary colors.

What is Colour?

Colour is a type of information our eyes receive and process based on electromagnetic radiation.

• Absorption, Reflection, and Scattering: An object doesn’t inherently have a colour. 
  • When light hits an object, it interacts with the object’s surface.
    • Then, it absorbs, reflects, and/or scatters different frequencies of visible-light radiation. 
    • Our perception of color arises from these interactions.

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How Human Eyes Process Colour?

• Rod and Cone cells: The human eye contains rod and cone cells that process light information.
  • Rod cells detect brightness.
  • Cone cells detect wavelengths, which the brain interprets as color.
• Humans have three types of cone cells, each sensitive to different wavelengths.
  • It allows us to see a range of colors.
• Trichromats: This ability to see three wavelengths is why humans are called trichromats.

Vision in Other Species

• Tetrachromats: Many birds and reptiles are tetrachromats, meaning they have four types of cone cells.
• Visible wavelengths: Humans can see wavelengths from 400 nm to 700 nm, known as visible light.
• Ultraviolet light: Some animals, like honeybees, can see ultraviolet light.
• Infrared radiation: Mosquitoes and some beetles can sense infrared radiation, which humans feel as heat.

Limitations and Enhancements in Viewing Celestial Images

• Visible spectrum:Human vision limitations mean we can’t see beyond visible light.
• False colors: Space telescope images often use false colors to highlight information in radio waves, X-rays, gamma rays, and ultraviolet light.
  • Without these enhancements, celestial images would show much less detail in visible light alone.

Methods of Rendering Colors

• Additive Coloring
  • In additive coloring, different wavelengths of light are combined to create a new color.
    • This method is used in devices like smartphone screens and televisions.
  • The RGB color space is a common example:
    • Red, green, and blue light are mixed in varying amounts to produce other colors.
• Subtractive Coloring
  • Subtractive coloring involves passing white light through a medium that absorbs certain wavelengths, leaving the rest to create a specific color.
    • Examples: dyes, pigments, and inks.

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Examples of Colour’s Influence

• Prehistoric Use of Ochre
  • Humans used ochre in ancient times. 
  • Mixture for Ochre: The formation of ochre involves mixing ferric oxide, clay, and sand correctly.
• Development of Blue LEDs
  • Red and green LEDs existed in the 1970s, but no blue.
    • Without blue, white light (ideal for homes and industry) couldn’t be made.