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A Complete Guide to Colour Blindness

Posted on July 14th, 2022

The ins and outs of colour deficiency, including what causes it, and how it can be treated.

There are at least 1.7 million Canadians who see colours differently than most people. Colour blindness is a common condition that mostly impacts men, and those who experience it often have trouble distinguishing between shades of red, yellow, brown and green. 

There are various types of colour blindness, the most common of which is genetic. Whether you experience colour blindness or not, the likelihood is that you know someone who does, and either way, it’s an interesting topic worth exploring and understanding. 

FYidoctors’ very own Dr. Ben Wild is sharing fascinating insight on the phenomenon of colour blindness, and how—to some extent—we all see the world a little differently.  

The basics of colour blindness  

Colour blindness—also called colour deficiency—is a condition in which an individual is unable to see colours in a “normal” fashion. In most cases, it impacts both eyes, and typically, someone who is colourblind struggles to distinguish between specific shades, and certain colours can appear skewed.  

“It all stems from light energy,” Dr. Wild explains. “The perception of colour is completely made up in our brains.” 

That means people have the propensity to see the same colour in an entirely different manner. 

“The cool thing about colour is that 96% of people agree on colours,” Dr. Wild says. The remaining 4%, he adds, are those who are deemed colour deficient.  

What causes colour blindness?  

There are a number of factors that can contribute to colour blindness.  

“It can actually be affected by things as small as the size of your pupil,” Dr. Wild says. “The bigger the pupil, the harder it is to discern colours.” 

The retina also plays a critical role.  

There are two types of cells in the retina—called rods and cones—that detect light. While rods sense light and dark, cones detect colour. Our brains rely on information from three types of cone cells to influence our perception of colours.  

Naturally, when one (or more) cone cell type is not functioning properly (or is absent altogether), our colour perception is thrown off. There are varying degrees of colour blindness, and the level of severity is often tied to the number of cone cells that are absent or malfunctioning. For example, if all three cone cells are abnormal, severe colour blindness is likely. On the flip side, if all three cone cells are functioning properly, a person can usually distinguish colours with ease. 

But, as Dr. Wild points out, everyone sees colour a little bit differently—regardless of their cone capacity. 

“Even if two different people have the exact same type of cones in the retina, it is still highly unlikely that they would actually see colours the same way,” he says. “That's because the brain plays a huge role in trying to figure out what colour you're actually seeing.”  

Different types of colour blindness  

As mentioned above, colour blindness can take many forms, but the condition can generally be divided into three different degrees: mild, moderate and severe.  

On the severe end of the spectrum, some people struggle to see colour all together. Although this form of colour blindness—called achromatopsia or monochromacy—is very rare, some people solely see shades of grey. Achromatopsia is generally associated with amblyopia (lazy eye), light sensitivity, poor vision, and nystagmus.  

“Those are the true colorblind people,” Dr. Wild explains. “They can't see any colours at all.” 

On the flip side, mild colour deficiencies means a person can see colours normally when the light is good, but in darkness, they struggle to differentiate between colours. Mild colour blindness can be so faint, in fact, that many people who have it are unaware that they do.  

In any case, colour blindness is usually genetic, and is often passed on from a mother to a son.  

There are three main categories of colour blindness, including red-green, blue-yellow, and complete colour blindness. In the first two types, a person tends to confuse the two colours mentioned, though each group has its own set of colour deficiencies.  


- Deuteranomaly: greens will have more of a red shade  

- Protanomaly: reds will look more green and less bright  

- Protanopia and deuteranopia: reds and greens are indistinguishable 


- Tritanomaly: blue and green are difficult to distinguish, as well as red and yellow 

- Tritanopia: all colours appear less bright, and it’s hard to differentiate between several combinations of colours such as blue and green, purple and red, and yellow and pink 

When does colour blindness start and what can trigger it? 

Colour blindness generally starts at birth as a congenital condition, though it can also materialize later in life as a result of trauma, disease (mainly metabolic or vascular issues) or drugs.  

Disease-induced colour blindness is not as widely studied as congenital colour blindness. In most cases, disease-specific vision concerns get worse over time. Colour deficiencies can also be caused by damage to the retina or optic nerve, which can occur in an accident.  

Other eye conditions, such as “cataracts, macular degeneration, and even blurry vision can actually make it difficult to discern colours,” Dr. Wild says. 

Plus, he adds, staring into the sun for extended periods can also cause colour blindness.  

“You can actually burn some of your photoreceptors and make it hard to determine colour,” Dr. Wild warns. 

(Reminder: Wear your sunglasses! Shop our amazing selection of shades here.) 

Colour blindness symptoms  

- Trouble distinguishing between colours, and shades of the same colour  

- Inability to see certain colours as others do  

The good news is, colour blindness typically does not impact vision clarity. Given that colour deficiencies are most commonly present at birth, there are certain signs that parents should look out for in their children to detect colour blindness. Although the condition is not preventable, there are special colour vision glasses, contact lenses and other mechanisms available that can help address the condition. 

The main indicator of colour blindness in toddlers is mixing up colours when painting or drawing. Specifically, colour deficient kids will likely have difficulty distinguishing between red and green, so that’s definitely something to look out for. If you start to notice colour confusion in your child, be sure to schedule them for a comprehensive eye exam.  

Why are men more at risk? 

While colour blindness is relatively uncommon in women (it impacts 1 in 200), it is far more prevalent in males, affecting 1 in 12 men. The reason men are substantially more susceptible to colour deficiencies is because most gene mutations that cause colour blindness are carried on the X chromosome.  

As we explained in a previous article on this topic, females have two X chromosomes, so if they have one that is unaffected, they will only be carriers. To be at risk of inheriting the disorder, females would need both a carrier mother and an affected father. Conversely, males only have one X chromosome that is inherited from the mother’s side. If that chromosome is affected, the male child will be colour blind. 


Colour blindness can be easily diagnosed through a regular eye examination using various colour tests. If you are experiencing any of the aforementioned symptoms, it’s important to confirm a diagnosis with your doctor. Book a comprehensive eye exam today at an FYidoctors location near you!  


At present, there is unfortunately no cure for colour blindness, but research in the field is expanding. There are a number of promising new discoveries—such as a gene therapy that has been developed to cure colour blindness in monkeys. Stay tuned for more developments in this space. 

As we await further advancements, there are special glasses and coloured contact lenses that can address vision deficiencies. There are also digital apps designed to help colour blind users identify certain colours.  

It’s always best practice to consult with your doctor about your personal eye care needs, and always be sure to stay up to date with yearly eye exams.