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Colour vision (colour blindness)
Colour vision deficiency — often called colour blindness — means seeing certain colours differently, most commonly reds and greens. It is usually inherited and affects roughly 1 in 12 men and about 1 in 200 women.
These are self-screening tools for general awareness, not a medical diagnosis. Screen brightness, colour calibration and room lighting all change what you see. See an optometrist or ophthalmologist for any real concern, for a proper eye test, and urgently if vision changes suddenly.
How the plate test works
The familiar test uses pseudo-isochromatic plates: circles filled with coloured dots where a number or path is hidden in a different hue. Someone with typical colour vision reads one figure; someone with a red–green deficiency reads another, or none. It is quick and good at flagging the common inherited types.
What it can and cannot tell you
An online version can hint that your colour vision differs, but a phone or laptop screen is not colour-calibrated, and room lighting changes what you see, so the result is only a rough screen. It cannot grade how strong a deficiency is or tell an inherited type from one caused by an eye or nerve condition. An optometrist uses calibrated plates and instruments like an anomaloscope for that.
Living with it
Most people with inherited colour vision deficiency adapt well. It mainly matters for a few colour-critical jobs (some aviation, rail and electrical roles) and for everyday design choices. If a deficiency appears suddenly or in one eye only, that is different — see an eye doctor promptly, as it can signal another problem.
Other eye checks
Contrast sensitivity
Not the same as sharpness — how well you tell subtle shades apart, which matters for night driving and fog.
Near vision and reading
Why small print gets harder from your forties, and what a reading check does.
Astigmatism
When the eye is shaped more like a rugby ball than a football, blurring near and far.
The Amsler grid
A simple grid used to watch the central retina — wavy or missing lines are a reason to act.
Source: General optometry references. A screen-based check is not a diagnosis — see an optometrist or ophthalmologist. · checked 2026-09-04
Frequently asked questions
Is colour blindness curable?
Inherited colour vision deficiency is lifelong and not curable, though special filters help some people distinguish certain colours. A deficiency that appears suddenly may be due to a treatable cause and should be checked.
Why does the online test give different results each time?
Screen brightness, colour profile and surrounding light all change how the plates look, so an uncalibrated online test is only a rough screen. A clinic uses standardised plates and lighting.
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