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When Red Goes Rogue: The Curious Science of Colour Vision

by | Oct 1, 2026 | Manuscripts | 0 comments

Jeba Ahmed (1), M. Optom. Student

Haziel Rynjah (2), Assistant Professor,

Royal Global University, Assam, India

 

Keywords

colour vision deficiency, cone photoreceptors, colour perception, genes coding.

Declaration of Interest

No conflict of interest.

The Traffic Light That Was Not Red

Imagine running up to a traffic signal and braking because the red light looked so much like the green one, or grabbing at a nice red apple, only to find out a second too late that you picked up an unripe one. Yet, for the millions of people around the world who suffer from Colour Vision Deficiency (CVD), this is a rather common challenge. Contrary to the name, colour blindness does not mean total inability to perceive colours, it means that colour vision is impaired, restricting their capability to perform some tasks that seem trivial for the rest of us. (1)

The Science of the Rainbow

We can see a wonderful world around us because we have three types of cone photoreceptors in my retina. They are known as L, M, and S cones and respond to long, medium, and short wavelengths of light. If the function or spectral sensitivity of these cone photopigments is altered or absent, the ability to discriminate between certain colours may be impaired. The most common example is the inability to discriminate between red and green colour present in millions of people worldwide.  (1,2)

When Genes Get Painted

The majority of genetic cases of colour vision defects are caused by the malfunction of genes coding for the opsins in cone cells, resulting in their inability to perceive particular colours appropriately. (3,4)

  

Figure 1: This image shows the Genetic Palette of Colour Vision.

Image Courtesy : https://images.pexels.com/photos/12489164/pexels-photo-12489164.jpeg

Living in a Colour-Coded World

Modern life depends heavily on colour. Traffic lights, medicine instructions, school charts, maps, and safety signs are common sights in our lives. Steward and Cole explain that many CVD patients have difficulties performing these daily tasks, although most adapt by using other visual hints such as brightness, shape, position, or context instead of colours. (5)

Why Early Detection Matters

Although there is no treatment for most cases of inherited colour vision deficiency, early diagnosis is important. Diagnosis of CVD in childhood helps teachers modify instructions, parents understand their child’s limitations, and Optometrists counsel about career choices. For eye care professionals, the diagnosis of colour vision deficiencies is much more than a demonstration of an abnormal Ishihara plate. It is also an educational opportunity to help patients understand that many things in the environment are not as they appear to be and to encourage alternative methods of communication wherever colour is used. (5,6)

Conclusion

Seeing the world in all its colours is a powerful tool, but many people do not realise that colour is a language that communicates beyond itself. Warnings, approvals, feelings. All can mean something different through the visual spectrum.Colour enables us to perceive the world around us; it is part of our language, helping us understand the world. The fact that people have different views on colours reminds us that although some cannot perceive colours as we do, they can lead happy lives if diagnosed early and educated about the deficiency. After all, when red turns grey, the world looks beautiful. (5)

If you see red, the next time, consider what that could mean to someone with Colour Vision Deficiency. 

Reference

  1. Birch J. Diagnosis of defective colour vision. Oxford: Butterworth-Heinemann; 1993.
  2. Simunovic MP. Colour vision deficiency. Eye. 2010 May;24(5):747-55.
  3. Neitz J, Neitz M. The genetics of normal and defective color vision. Vision research. 2011 Apr 13;51(7):633-51.
  4. Deeb SS. Molecular genetics of colour vision deficiencies. Clinical and Experimental Optometry. 2004 Jul;87(4‐5):224-9.
  5. Steward JM, Cole BL. What do color vision defectives say about everyday tasks?. Optometry and vision science. 1989 May 1;66(5):288-95.
  6. Sharpe LT, Stockman A, Jägle H, Nathans J. Opsin genes, cone photopigments and color vision. In: Gegenfurtner KR, Sharpe LT, editors. Color vision: from genes to perception. Cambridge: Cambridge University Press; 1999. p. 3-51.

About the Author

Jeba Ahmed

M. Optom Student,

 

The Assam Royal Global University, Guwahati, India

Haziel Rynjah

Assistant Professor,

 

The Assam Royal Global University, Guwahati, India

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