Colour Blindness or Colour Vision Deficiency

Most of us take it for granted but for some, recognizing colours is an impossible task.

By Evangeline Majawat


As a toddler, Yaw Shoong Lee threw a huge tantrum every time he was asked to eat the fruits and vegetables on his plate. Tomatoes, apples, broccoli and oranges were just some of the food that he absolutely disliked and cried hysterically if his mother or nanny tried to coax him to eat it.

“My parents and grandmother thought I was a fussy eater. When I grew older, they would punish me if I didn’t eat my fruits and vegetables. So, I learnt to like those foods,” the now 31-year-old Yaw explains.

It was only when he was six did Yaw’s parents suspect something was wrong and discovered that their son could not identify colours properly. “It was our the sports day at my kindergarten. There was a game where we had to group some toys, which were in a pile, according to the colours. Apparently, I heaped the green and red ones together. My mum said it looked like a Christmas decor pile!” jokes Yaw.

A trip to the family doctor and later to the ophthalmologist confirmed his parents’ suspicion. Yaw was diagnosed with red-green colour blindness. “It all made sense to everyone then. I was a fussy eater because certain fruits and vegetables looked disgusting to me. I had to keep telling myself that vegetables and fruits are good for me and to learn to eat them,” Yaw says, laughing. “They still don’t look palatable but I’ve learned to like them.”


What Is Colour Blindness?

The correct term for colour blindness is colour vision deficiency (CVD). It is also known as Daltonism, after the scientist John Dalton.“The term colour blindness is misleading because people automatically assume that the person can’t see colours at all or that he or she sees everything in shades of grey,” says Queen Elizabeth Hospital ophthalmology department specialist Dr K.V. Chin. “But it’s not true.”

CVD is a hereditary condition, usually inherited from the mother. The genetic mutation that causes CVD is carried in the X chromosome. Men have one X and Y chromosome, which is why occurrences of CVD are more common in men. Approximately 1 in 12 men are colour blind compared to the 1 in 200 women who have the condition.

Dr. Chin explains that the retina in our eyes has two types of light-sensitive cells called rods and cones. Rods help in night vision while cones are responsible for colour recognition.

There are three different types of cone cells. Each cone detects different colour wavelengths; red, blue and green. A person sees colour correctly if he or she is able to detect all three colours.

“Our eyes work like a camera. An image is formed when light enters our eyes and stimulates the retina. This is where the rods and cones are,” explains Dr. Chin. “The cones are the ones that affect whether one can detect the colours. A person is mildly or severely colour blind depending on how faulty his (or her) cones are.”

But, he points out that colour blindness can also be developed from illnesses, ageing and as side effects from certain medicines. Diabetes, glaucoma, sickle-cell anemia and inflammation of the optic nerve can cause CVD.

According to the United Kingdom’s National Health Trust, there are two types of CVD.


  • Red-green deficiency – where people are unable to distinguish certain shades of red and green; it is the most commonly inherited type.
  • Blue-yellow deficiency – this is a rare condition where it is difficult to distinguish between blue and green. Yellow may appear as a pale grey or purple.


“Some people only realise they are colour blind when they go for an eye test,” says Dr. Chin. “Parents usually find out quite early on if their kids have the condition because the kids usually fail at colour-related activities.” However, he reassures that CVD is definitely not a life-endangering condition.


The Colour Test

The Ishihara Colour Perception Test is still the standard examination to detect CVD. Japanese professor Dr. Shinobu Ishihara designed a series of coloured plates. Each plate consists of random dots that form numbers and lines, which are only visible if a person can differentiate similar hues.

“It’s a very simple test but quite accurate. This test is used during standard health checks and when applying for a driver’s license,” states Dr. Chin. He adds that CVD can also be diagnosed using the arrangement test where a person is required to arrange coloured objects according to different hues.

While CVD is a harmless condition, it is not curable. “Currently, there is no known cure. Recent studies have suggested that gene therapy can help but this is currently in the early (research) stages,” he shares.

In 2009, scientists in the United States restored full colour vision in adult monkeys that were unable to detect red and green colours. The team injected ‘therapeutic genes’ into the monkeys’ retina over a span of two years. The scientists claimed the mission was a success and were hopeful that a similar therapy can be made available for humans soon.

Ophthalmologists sometimes prescribe tinted contact lenses to help detect colours easily but Dr. Chin says this does not always work for everyone.


Tint My World

As he entered his early adult years, Yaw realised that his colour blindness would affect his fashion sense and personal style. “It hit me when I entered secondary school. This was when you hit puberty and start noticing the opposite sex. I was so worried about bumping into my friends outside of school especially the girls!” says Yaw. So, he stuck to the basics of white and black t-shirts and jeans.

“I was into the baggy trousers and t-shirt era of the 90s but I didn’t dare wear any coloured clothes because I didn’t want to look like a clown,” he recalls. “I got my siblings to help me choose my clothes if I had to wear anything colourful.”

Colour Blind Awareness, an Australian-based community interest company, works hard to raise awareness about difficulties faced by those who have CVD. The website states that, “Colour blind people face many difficulties in everyday life which normally sighted people are just not aware of. Problems can arise in performing even the most simple activities including choosing and preparing food, gardening, sports, driving a car and selecting clothing. Colour blind people can also find themselves in trouble because they haven’t been able to pick up a change in someone’s mood by the subtle change in the colour of their face or not noticed their child getting sunburned.”

Everyday activities that a colour blind person will find hard to do include telling the difference between cooked and raw meat and reading traffic lights correctly. Contrary to popular belief, those with CVD are allowed to drive but not commercially.

Colour Blind Awareness also emphasises that colour blind people can learn to live with the condition. It is important for severely colour blind people to get their family and friends involved in everyday tasks that they find challenging. Loved ones can pick clothes and coloured items for the person who struggles with recognizing colours. It is believed that the wife of Britain’s Foreign Secretary William Hague, who is reportedly colour blind, pins labels to his clothes whenever she is not travelling with him.

Good lighting in the home and workplace may also help a colour blind person to distinguish colours. As for Yaw, he does not feel that CVD has tremendously affected his life. “It’s something I have and I deal with it. It’s more of an inconvenience to me and my family because they need to help me choose my clothes. I can’t be a pilot but life goes on,” he says jovially.


Working with colours

Some jobs do not take on those who are colour blind. These jobs require accurate colour recognition. The list below details some of the jobs that require normal vision.

However, some organisations and institutions do accept colour blind people depending on the severity of the condition.

  • Commercial pilot
  • Baggage handler
  • Police officer
  • Fireman
  • Graphic designer
  • Electrician
  • Military – You won’t be able to carry out certain jobs


Famous people with CVD

Here are some prominent colour blind personalities who made their mark in the world.

  1. Mark Twain, American author
  2. Bill Clinton, former US President
  3. Keanu Reeves, Actor
  4. Bing Crossby, Actor and Singer
  5. Matt Lauer, Actor
  6. Christopher Nolan, Director of Batman (The Dark Knight and The Dark Knight Rises) and Inception
  7. Vincent Van Gogh, Post-Impressionist artist. – A Japanese vision expert recently developed a tool that found that Van Gogh most probably colour blind and had glaucoma.
  8. Albert Uderzo, Creator of the cartoon Asterix and Obelix

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