Ask a painter, a pilot, or a fabric designer why colour vision matters, and you will hear a dozen answers. For most of us, colours feel so automatic that we rarely think about them. Until the day someone casually points out that a jumper you thought was green actually looks quite brown, or a child confuses red and green traffic signals, and the question surfaces: do my eyes see colour the way everyone else’s do?
Colour vision tests are simple, quick, and widely available. This guide walks you through what they measure, how they work, and why they matter.
How Does Colour Vision Work?
Colour vision depends on three types of cone cells in the retina.
- Red-sensitive cones (L-cones)
- Green-sensitive cones (M-cones)
- Blue-sensitive cones (S-cones)
The brain combines signals from these cones to generate colour perception. If any cone type is missing, abnormal, or functionally reduced, colour vision changes.
What Is a Colour Vision Test?
A colour vision test is a clinical procedure that assesses the ability to perceive and differentiate colours. It is used to:
- Detect congenital colour vision deficiency
- Identify acquired colour vision loss from eye or brain conditions
- Screen for career eligibility in pilots, drivers, defence, and electricians
- Monitor disease progression in retinal or optic nerve disorders
- Evaluate toxicity from certain medicines
- Assess children with learning or visual concerns
Types of Colour Vision Deficiency
1. Protanopia
Red-blindness; L-cone absent or dysfunctional.
2. Deuteranopia
Green-blindness; M-cone absent or dysfunctional.
3. Tritanopia
Blue-blindness; S-cone absent or dysfunctional (rare).
4. Anomalous trichromacy
Partial loss in one cone type, the most common form.
5. Monochromacy
Total colour blindness; extremely rare.
6. Acquired colour vision deficiency
From eye disease, optic nerve disease, or brain conditions.
Common Colour Vision Tests
1. Ishihara plates
The classic test. Patients identify numbers or patterns hidden in dots of different colours. Quick, widely used, and reliable for red-green deficiency.
2. Farnsworth D-15
Arranging 15 colour caps in order. Identifies both severity and type of colour vision deficiency.
3. Farnsworth-Munsell 100-hue test
A more detailed version using 100 colour caps. Useful for occupational screening and acquired deficiencies.
4. HRR (Hardy-Rand-Rittler) plates
Similar to Ishihara but designed to classify severity and type.
5. Anomaloscope
A precise device that asks patients to match colours using knobs. Used in specialist settings.
6. Cambridge Colour Test
A computer-based test with high precision, useful in research and advanced clinical settings.
7. City University test
Another colour-matching test.
8. Online screening tests
Useful for rough screening but not a substitute for in-clinic testing.
Who Should Take a Colour Vision Test?
- Children with suspected colour confusion
- Adults entering colour-sensitive careers
- Patients with new vision changes
- People with optic neuritis, glaucoma, retinitis pigmentosa, diabetic retinopathy
- Patients on medications that can affect colour vision (ethambutol, hydroxychloroquine, digoxin)
- Those with a family history of colour vision deficiency
- Anyone applying for defence, police, pilot, or railway services where required
How Is a Colour Vision Test Performed?
The test is quick and painless.
For Ishihara plates
- Sit comfortably in good daylight or standardised clinic lighting
- The examiner shows plates one by one
- You read aloud the number or trace the pattern
- The examiner records correct and incorrect answers
- Total time: 3 to 5 minutes
For Farnsworth tests
- A set of colour caps is presented in random order
- You arrange them in a smooth colour sequence
- The examiner records the pattern
- Results are plotted and interpreted
- Total time: 5 to 10 minutes
For anomaloscope
- The patient sits at the device
- Matches a test colour to a mix of other colours using knobs
- The examiner records the matches
- Useful in specialist work-ups
Children often use age-appropriate tests with pictures instead of numbers.
What Do the Results Mean?
Normal colour vision
Most plates read correctly or all caps arranged properly.
Anomalous trichromacy
Mild to moderate confusion, usually in the red-green range. Many patients manage daily life well but may struggle with certain tasks.
Dichromacy
Significant loss of one cone type; more pronounced confusion.
Monochromacy
Severe colour vision loss; rare.
Acquired patterns
Certain patterns (e.g. blue-yellow loss) suggest optic nerve or retinal disease.
Your eye doctor at an eye specialist hospital will explain the exact implications of your result.
How Common Is Colour Vision Deficiency?
- About 8% of men and 0.5% of women have some form of colour vision deficiency
- Red-green deficiency is the most common type
- Blue deficiency is rare
- Congenital deficiency is usually stable throughout life
- Acquired deficiency may progress or reverse depending on the cause
Common Causes of Acquired Colour Vision Deficiency
- Optic neuritis
- Glaucoma
- Diabetic retinopathy
- Age-related macular degeneration
- Cataract (yellow nuclear cataract distorts colour perception)
- Retinitis pigmentosa
- Multiple sclerosis
- Medication side effects
- Head injury
- Stroke affecting visual pathways
Supportive eye treatments for the underlying condition may improve colour vision in acquired cases.
Can Colour Vision Deficiency Be Treated?
Congenital colour vision deficiency usually cannot be “cured”. Supportive options include:
- Colour-correcting glasses and lenses (e.g. EnChroma)
- Smartphone apps that label colours
- Colour-coded organisation systems
- Career counselling for affected individuals
- Regular follow-up to rule out acquired changes
Acquired colour vision deficiency is treated by addressing the underlying cause.
Colour Vision and Career Requirements
Certain careers in India require specific colour vision standards.
- Defence services
- Commercial pilots
- Merchant navy
- Railways
- Some police services
- Certain electrical and chemical engineering roles
- Certain textile and printing roles
A formal colour vision test at an accredited eye hospital is often part of career medicals.
Children and Colour Vision
- First test around age 5 to 6, or earlier if suspected
- Age-appropriate testing with picture-based plates
- School performance review if colour confusion affects learning
- Parents informed about career implications
- Regular checks if a family history exists
Tips for Living With Colour Vision Deficiency
- Label clothes and objects by category
- Use apps that identify colours
- Ask trusted friends or family for help when needed
- Use high-contrast settings on screens and devices
- Inform employers or teachers where relevant
- Choose colour-coded tools carefully
Preparation Tips for the Test
- Bring your current glasses if you wear them
- Avoid tinted contact lenses
- Note any medicines that affect colour vision
- Be well-rested; fatigue can affect results
- Mention any family history of colour deficiency
- Be candid with the examiner about any guessing
When Should You See a Doctor?
Book a test if:
- You suspect you or your child has colour confusion
- You are preparing for a career that requires colour vision
- You have new vision changes, especially after illness or medicine
- You have a known optic nerve or retinal condition
- You have diabetes, MS, or glaucoma
- You have had a head injury
- You want a baseline test before starting ethambutol or similar drugs
Colour Vision Care at Vasan Eye Care
Vasan Eye Care has been looking after patients across India since 2002, now as part of ASG Enterprises. With more than 150 super-speciality centres, 500+ ophthalmologists, and over 5,000 trained eye care staff, the team routinely performs colour vision tests for clinical and career screening. A typical visit includes the test itself, along with a full eye examination to rule out underlying conditions.
Key Takeaways
- Colour vision tests check how well the eyes and brain perceive colours.
- Common tests include Ishihara plates, Farnsworth tests, and anomaloscope.
- Congenital colour vision deficiency affects about 8% of men and 0.5% of women.
- Acquired colour vision loss can signal eye or neurological disease.
- Specific careers require formal colour vision screening.
- Supportive options exist for those with colour vision deficiency.
Frequently Asked Questions
A colour vision test is a simple clinical procedure that measures how accurately you perceive colours. It uses plates with coloured dots (Ishihara), coloured caps arranged in order (Farnsworth), or precise devices (anomaloscope). The test identifies congenital colour vision deficiency, screens for career eligibility, and detects acquired colour loss from eye, nerve, or systemic conditions. Most tests take a few minutes.
The most common version uses Ishihara plates showing numbers hidden in coloured dots. Patients with normal colour vision read the numbers correctly. Those with colour vision deficiency misread or cannot see certain numbers. More detailed tests use coloured caps arranged in a specific order, which identifies both the type and the severity of colour vision loss.
Children with suspected colour confusion, adults entering colour-sensitive careers, patients with new vision changes, people with certain eye or neurological conditions, and patients taking medicines that can affect colour vision (ethambutol, hydroxychloroquine, digoxin) all benefit from testing. A family history of colour vision deficiency is also a good reason to test.
Congenital colour vision deficiency usually cannot be reversed. Colour-correcting glasses and lenses offer partial improvement in some people, and smartphone apps can help with daily tasks. Acquired colour vision loss from optic nerve or retinal disease may improve when the underlying condition is treated. Regular follow-up tracks any change over time.
References
- American Academy of Ophthalmology. Colour Blindness. https://www.aao.org/eye-health/diseases/what-is-color-blindness
- National Center for Biotechnology Information. Colour Vision Testing. https://www.ncbi.nlm.nih.gov/books/NBK585068/
- National Eye Institute. Colour Blindness. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/color-blindness
- WebMD. Colour Vision Test. https://www.webmd.com/eye-health/color-vision-test
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