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Health condition

Colour blindness, the types, the tests and what actually helps.

Common, stable and largely inherited. Understanding the pattern, using the right tools and knowing when a change needs review is most of what matters.

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Why trust this guide

  • 01

    Editorial team

    Written by our editorial team from the UK sources listed on each page.

  • 02

    Sourced from guidance

    Checked against the Royal College of Ophthalmologists, NHS and peer-reviewed sources you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice on Ishihara testing, corrective lenses and occupational advice.

Key facts

Colour blindness at a glance.

The essentials, in plain English - what it is, who gets it, how it is tested and what actually helps in daily life.

  • What it is

    Colour vision deficiency (CVD) - a reduced ability to distinguish certain colours because of altered cone-cell photopigments in the retina.

  • How common

    Red-green CVD affects roughly 8% of men and 0.5% of women in populations of European descent - it is largely X-linked recessive.

  • Types

    Red-green (protan and deutan) is the common inherited form. Blue-yellow (tritan) is rare. Complete monochromacy is very rare.

  • Acquired CVD

    Glaucoma, macular degeneration, optic neuritis, diabetes and certain drugs (ethambutol, hydroxychloroquine) can cause later-onset colour changes.

  • How it is tested

    Ishihara plates for screening, Farnsworth D-15 for sorting, anomaloscope for precision, and genetic testing where relevant.

  • Management

    No cure. Coping strategies, apps, tinted lenses (subjective benefit only) and occupational counselling all help.

Why this guide matters

A stable condition with a few load-bearing decisions.

Inherited colour blindness is common, stable and non-progressive. But acquired colour change and career choices need clear thinking.

  • Get a formal diagnosis

    Knowing the type - protan or deutan - and the severity is useful for coping strategies, occupational advice and family planning.

  • Separate inherited from acquired

    New colour change in adulthood is not inherited CVD. It deserves an eye examination for glaucoma, macular disease or drug toxicity.

  • Think about careers early

    Some roles have statutory colour standards. An honest conversation with a young person prevents later disappointment.

How the diagnosis is made

From first suspicion to a clear report.

The steps a UK optometrist or ophthalmologist will normally follow, in order - so you know what to expect and why.

  1. 01

    Screening

    History and family pattern

    A careful history - onset, colours confused, medications and family history - often points to inherited red-green CVD.

  2. 02

    Screening

    Ishihara plate screening

    The pseudoisochromatic plates are the standard first-line screen for red-green CVD in schools, opticians and occupational health.

  3. 03

    Screening

    Rule out acquired causes

    A dilated fundus check looks for glaucoma, macular disease and optic neuropathy - especially with sudden or asymmetric colour change.

  4. 04

    Classifying

    Farnsworth D-15 arrangement

    A colour-arrangement test that separates protan from deutan and grades severity - useful when Ishihara is positive.

  5. 05

    Classifying

    Anomaloscope confirmation

    The reference standard for red-green CVD - a colour-matching instrument used in specialist and occupational settings.

  6. 06

    Advising

    Molecular genetic testing

    Reserved for atypical patterns, suspected monochromacy or when carrier status matters for family planning.

  7. 07

    Advising

    Occupational counselling

    A written report for the DVLA, aviation medical, rail or armed-forces role - honest about what the results allow.

Typical timeline: a first visit to a clear diagnosis in a single appointment for most people.

Symptoms

What colour blindness actually feels like.

A mix of everyday frustrations, a few genuine safety issues and - importantly - the signals that mean it is time to see an ophthalmologist.

  • Traffic-light confusion

    Difficulty distinguishing red and green signals, especially at distance or in poor light - the most common everyday complaint.

  • Fruit and food

    Trouble judging ripeness of tomatoes, strawberries or bananas, and telling cooked from raw meat by colour alone.

  • Charts and graphs

    Colour-coded slides, spreadsheets and maps become hard to read - a workplace and school issue.

  • Fashion and matching

    Difficulty pairing clothes and choosing paint or furnishings - a lifelong source of frustration.

  • Electrical wiring

    Standard red, brown, blue and green cables can be indistinguishable - a genuine safety issue for DIY and trade work.

  • Often unaware

    Many people with mild CVD are undiagnosed until a school test, a driving eye check or a workplace screening flags it.

  • Later-onset change

    New colour disturbance in adulthood is different - it points to acquired eye disease or drug toxicity and deserves review.

  • Red flag - sudden change

    Sudden loss of colour vision, especially with pain or visual loss, needs same-day ophthalmology assessment.

Management

How colour blindness is managed in the UK.

There is no cure. But a clear diagnosis, sensible tools, honest careers advice and treatment of any acquired cause make a real difference.

  • Education and reassurance

    For most inherited red-green CVD, understanding the condition is the single most useful intervention. It is stable and non-progressive.

  • Coping strategies

    Learning traffic-light position, labelling clothes and food, and asking a trusted person for a second opinion on key colour decisions.

  • Smartphone apps

    Colour Blind Pal and Chromatic Vision Simulator name colours in real time and can simulate how others see - useful for daily tasks and design work.

  • EnChroma lenses

    Selective-notch filter glasses that some people find enhance red-green contrast. Benefit is subjective and not universal - trial before buying.

  • Pilestone corrective lenses

    Alternative tinted lens ranges with indoor and outdoor options. Same caveat - subjective and no guaranteed effect on formal tests.

  • Occupational counselling

    A frank conversation about careers with statutory colour requirements - pilot, train driver, some armed-forces roles, electrician.

  • Genetic counselling

    For families planning children - explains X-linked recessive inheritance, carrier status in daughters and risk to sons.

  • Treat the underlying cause

    For acquired CVD - manage glaucoma, macular disease or diabetes, and review culprit drugs such as ethambutol or hydroxychloroquine with the prescriber.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your optometrist or ophthalmologist knows your eyes and history and can tell you which parts apply to you. If in doubt, get seen.

  • Royal College of Ophthalmologists. Guidance on colour vision assessment.

  • NHS. Colour vision deficiency - patient information.

  • Colour Blind Awareness. Prevalence and everyday impact of CVD.

  • MHRA. Ocular monitoring guidance for hydroxychloroquine and ethambutol.

Red flags

When a colour change needs urgent attention.

Most inherited colour blindness is stable and needs no ongoing care. These are the situations that are different.

  • Sudden colour loss

    A new loss of colour vision - especially with pain, blur or a red eye - needs urgent same-day ophthalmology assessment.

  • Asymmetric change

    Colour vision worse in one eye than the other suggests optic nerve or retinal disease, not inherited CVD.

  • Red desaturation

    Reds looking washed out in one eye is a classic sign of optic neuritis and warrants prompt neuro-ophthalmology review.

  • Central visual loss

    Blurred central vision with colour change points to macular disease and needs prompt assessment.

  • Drug-induced toxicity

    Ethambutol and hydroxychloroquine can damage the optic nerve and retina - report new colour or vision change to the prescriber immediately.

  • Poorly controlled diabetes

    Colour disturbance can accompany diabetic retinopathy - review glycaemic control and retinal screening status.

  • Occupational implications

    Some roles have statutory colour standards - a positive test needs a formal occupational-health report before career decisions.

  • Complete achromatopsia

    Monochromacy with photophobia and nystagmus from childhood is a distinct genetic condition needing specialist paediatric ophthalmology.

  • Family planning concerns

    X-linked inheritance means daughters of an affected father are obligate carriers - genetic counselling helps clarify risk.

Living with it

A common condition, with practical answers.

Four things that make the biggest difference day to day - fixed cues, useful apps, openness at work and the reassurance that inherited CVD does not progress.

A quiet reminder

Small habits beat clever gadgets.

Learning position cues, labelling and asking for a second opinion when it matters solves most of the everyday problem.

  1. 01 Everyday

    Learn the fixed cues

    Traffic lights follow a fixed position, cooked meat has a fixed texture and appliance LEDs often have a fixed shape - lean on cues that are not colour.

  2. 02 Tools

    Use the apps

    Modern smartphone tools name colours in real time and are genuinely useful at the supermarket, in the wardrobe and in front of a chart.

  3. 03 Work

    Be open at work

    Ask colleagues for a colour check on slides and dashboards, and request pattern or label alternatives to colour-only coding.

  4. 04 Perspective

    It is stable and manageable

    Inherited CVD does not progress and does not damage the eye. A clear diagnosis and a few habits make a real difference.

Frequently asked

Everything we get asked about colour blindness.

Quick answers on inheritance, testing, tinted lenses and careers.

  • What is colour blindness?

    Colour vision deficiency (CVD) is a reduced ability to distinguish certain colours. The common inherited form is red-green CVD, caused by altered cone-cell photopigments and inherited in an X-linked recessive pattern - which is why it is much more common in men.

  • How common is it and who gets it?

    Red-green CVD affects roughly 8% of men and 0.5% of women in populations of European descent. Because the responsible genes sit on the X chromosome, sons of carrier mothers are at highest risk and daughters of affected fathers become carriers.

  • What are the different types?

    Red-green CVD splits into protan (protanopia, protanomaly - reduced red sensitivity, about 1% of men) and deutan (deuteranopia, deuteranomaly - reduced green sensitivity, about 6% of men). Blue-yellow (tritan) CVD is rare and autosomal. Complete monochromacy is very rare.

  • Can colour blindness develop later in life?

    Yes - acquired CVD can follow glaucoma, macular degeneration, optic neuritis, diabetes and certain drugs including ethambutol and hydroxychloroquine. Any new or asymmetric change in colour vision deserves an ophthalmology assessment rather than being assumed to be inherited.

  • How is it diagnosed?

    Ishihara pseudoisochromatic plates are the standard screening test. The Farnsworth D-15 arrangement test grades severity and separates protan from deutan. An anomaloscope is the reference standard and molecular genetic testing is reserved for atypical or rare presentations.

  • Is there any treatment?

    There is no cure for inherited CVD. Coping strategies, colour-naming apps and tinted lenses (EnChroma, Pilestone) help some people - benefit is subjective and does not change a formal Ishihara result. Career counselling matters where colour standards apply. For acquired CVD, treating the underlying cause is what changes outcomes.

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