Colour Blindness Test at Home: Signs in Children and Job Limits
The honest answer: an online colour blindness test at home can hint that something’s off, but it can’t confirm it. A proper check uses Ishihara plates or similar tests at an optometrist or eye doctor, it takes a few minutes, and it matters most before a child picks subjects and careers.
The short version
- Most common type: red-green colour vision deficiency, inherited, and far more common in boys.
- Home screens: phone apps and online plates vary with screen colour and brightness, so treat them as a hint only.
- Proper test: printed Ishihara plates in daylight-type light, done by an optometrist.
- Fixes: no glasses, eye drops, diet or exercise changes inherited colour vision.
- Careers: some jobs set colour vision standards, so check early.
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Your son colours the grass brown and the tree trunks green. His teacher shrugs. Creativity, or does he genuinely see colours differently? Around a family table in Pakistan or India this is often noticed late, sometimes only when a teenager who has spent years preparing for the air force, the merchant navy or an electrician’s diploma fails the colour plates at his medical and watches a plan he’d set his heart on quietly close. That’s the real cost. It’s avoidable.
What colour blindness really means
At the back of the eye, the retina has three kinds of colour-sensing cells called cones, one type tuned to red light, one to green and one to blue, and the brain compares their three signals to work out every colour you see, a bit like a painter mixing any shade from three tubes of paint.
In colour vision deficiency, one of those tubes is weak or missing. Most people with it aren’t “blind” to colour at all; they see plenty of colours but mix up certain pairs, most often reds and greens, browns and greens, or purples and blues. Total colour blindness is rare.
Did you know? The red and green cone genes sit on the X chromosome, and because boys have only one X, a single faulty copy is enough to show, while girls have two, so a healthy second copy usually covers for the faulty one. That’s why it runs from mothers to sons. Mothers with perfect colour vision can carry it.
Signs in children, by age
- Under 3 years: there’s no reliable way to spot it at home, and that’s fine. Nothing needs to be done this early.
- 3 to 6 years: trouble learning colour names long after other words, mixing up red and green crayons, picking odd colours for skin, grass or sky, or struggling with colour-coded worksheets.
- Over 6: difficulty reading coloured chalk on a green board, maps, graphs and charts in class, telling if meat is cooked, or spotting a red ball on grass in cricket.
Some children cope so well by using brightness and position that nobody notices for years. It isn’t laziness. It isn’t a learning problem.
Colour blindness test at home: what it can and can’t do
Online and app tests show dotted circles with a number hidden in them. Fine for curiosity. But phone and laptop screens all show colours differently, brightness and night-mode settings shift the result, and a child may simply guess or read the number off a helpful older sibling’s lips, so a “pass” at home doesn’t rule anything out and a “fail” doesn’t confirm anything either.
- Use daylight: sit by a window in daytime, screen at full brightness, night mode and blue-light filters off.
- One child at a time: no helpers whispering answers.
- Keep the distance: hold the screen about 75 cm away, roughly arm’s length for an adult.
- Note, don’t label: write down which plates were missed, then book a proper check.
For children who don’t know numbers yet, optometrists have picture and path-tracing versions. Most children can do a standard plate test from around age 5 or 6.
The Ishihara test at an optometrist
This is the everyday screening test: a book of printed plates is shown under good light, one eye at a time or both together, and the child reads the number or traces the winding line with a finger or a soft brush. A few minutes. No pain. If plates are missed, further tests (such as arrangement tests, where coloured caps are put in order) can show the type and how strong it is. Some job medicals use a lantern test too.
Many schools don’t screen for colour vision, so ask for it at a routine eye check. Our eye test schedule by age shows when those checks fall. Checking the colour vision of brothers and male cousins is sensible when one boy is found to have it.
Tinted “colour blind glasses” can make some colours pop for some people, which can feel lovely at a sunset, but they don’t restore normal colour vision and they won’t help anyone pass a colour vision medical. Carrots, badam, saunf and eye exercises do nothing for inherited colour vision either. The cones are built the way the genes built them. For the eyesight totkay that do and don’t work, see improve eyesight naturally.
School, driving and job limits
Most people with colour vision deficiency live, study and work with no trouble at all. A few areas deserve an early, calm look.
- School: tell teachers. Simple fixes help, such as labelling colours on crayons, using patterns in graphs, and white chalk on dark boards.
- Driving: most countries, Pakistan and India included, allow ordinary driving; people learn traffic lights by position. Rules for commercial and heavy vehicle licences can be stricter, so check the current rules where you live.
- Careers with standards: pilots, some armed forces and navy roles, railways, merchant navy, some police roles, electrical and electronics work (colour-coded wires), and some lab and textile jobs may set colour vision requirements. Rules differ by country and change over time, so check the official medical standards before choosing subjects.
- Medicine and design: many people with colour vision deficiency work as doctors, engineers and designers. They just learn workarounds.
Find out at 8, not at 18, and a career choice never gets taken away by surprise.
Inherited colour blindness is there from birth, affects both eyes the same and never changes. A colour change that is new, in one eye, or getting worse is different and needs an eye doctor soon. Colours looking washed out or faded in one eye, especially with pain on moving the eye or dimmer vision, can mean optic nerve inflammation and should be seen the same day. Some medicines, diabetes, glaucoma, cataract and certain thyroid eye problems can also change colour vision. Sudden loss of vision or a painful red eye always means a doctor the same day.
Colour blindness in children: common questions
How can I test for colour blindness at home?
Online plate tests on a bright screen in daylight can give a hint. They aren’t reliable enough to confirm it, so any missed plates should lead to an Ishihara test at an optometrist.
At what age can a child be tested for colour blindness?
Standard number plates usually work from about 5 or 6 years. Younger children can do picture or path-tracing versions at an optometrist.
Is colour blindness more common in boys?
Yes, much more.
Can girls be colour blind?
Yes, but it’s uncommon, because a girl usually needs the faulty gene from both sides of the family, meaning her father has it and her mother carries it, or else she has one of the other, rarer types that aren’t linked to the X chromosome at all.
Is colour blindness curable?
Inherited colour vision deficiency can’t be reversed with glasses, drops, food or exercises. Children learn to manage well with a few practical workarounds.
Do colour blind glasses work?
Not in the way the adverts suggest. They can sharpen contrast between some colours for some people, which many find pleasant, but vision doesn’t become normal and they won’t help anyone pass a colour vision medical for a job or licence.
Can a colour blind person get a driving licence?
For ordinary cars, usually yes, in Pakistan, India and most countries. Commercial and heavy vehicle licences can have stricter rules, so check the current local requirements.
Can a colour blind person join the army or become a pilot?
Some roles set colour vision standards and others don’t. Rules differ by branch and country, so check the official medical standards early, before choosing subjects.
Can a colour blind person become a doctor or engineer?
Many do. Some tasks need extra care or tools, but colour vision deficiency rarely blocks these careers entirely.
Can colour blindness get worse with age?
Inherited colour blindness stays the same. If colours seem to change or fade later in life, see an eye doctor, because cataract, glaucoma or other conditions may be the cause.
What is the Ishihara test?
A book of dotted plates with hidden numbers or lines, used under good light to screen for red-green colour vision deficiency.
How can teachers help a colour blind child?
Label colours in words, use patterns or shapes in charts, write in white or yellow chalk, and never mark a child down for “wrong” colouring.
More guides on children’s sight and routine checks are in our Eye Care section.