Colour Vision Test (Colour Blindness Screening)

A free colour blindness test you can take on any screen

This color blindness test screens for the two main kinds of colour vision deficiency: red-green (protan and deutan types) and the much rarer blue-yellow (tritan) type. It has two parts — 12 dot plates with a hidden number, in the style made famous by Dr Shinobu Ishihara, and a hue-arrangement task in which you put 15 coloured caps in order, based on the idea behind the Farnsworth D-15.

Every plate here is generated fresh in your browser by its own dot-pattern program; none is a copy of a printed test. The figure and the background are chosen so that they differ only in the signal of one type of cone in the eye, which is exactly the difference people with that cone missing or weakened cannot see.

It is a screening test, not a diagnosis. Screens are not calibrated, so a result here is a reason to see an optician or optometrist, not a substitute for one — especially if you need a result for work, a licence or school.

How to use the Colour Vision Test

1. Read the tips, turn off night mode and colour filters, and press Start the test.
2. For each of the 12 plates, type the number you see and press Next, or press I can’t see a number. Do not stare for long — a few seconds per plate is enough.
3. In part 2, tap the cap that looks most like the fixed cap on the left, then the one most like that, and so on until all 15 are placed. Tap a placed cap or use Undo last to change your mind.
4. Press See my result for a summary, an explanation of each part and a plate-by-plate table.
5. Take the test again in different lighting or on another screen if a result surprises you, and book an eye test if it suggests a deficiency.

Colour Vision Test features

How the plates are made

Colours are converted from sRGB into the responses of the three cone types (long, medium and short wavelength, often called L, M and S). For a red-green plate on the protan line, the number’s dots get a slightly higher L-cone signal than the background while M and S stay identical; for the deutan line only the M signal changes; for the blue-yellow tritan line only S changes. Someone with typical vision sees a clear change of hue — a colour difference of about 10 to 30 ΔE*ab — but a simulated dichromat on that line sees no difference at all.

The plates are graded: two in each set are easy, two are harder, so mild anomalous trichromacy can show up as misses on the faint ones only. The first plate is a demonstration plate with a large brightness difference that everybody should read; it checks that the screen and the answers are working.

Reading your result

• No sign of a deficiency: all plates read and the caps in order. Typical colour vision is likely, though very mild deficiencies can be missed on a screen.
• Probably normal: one or two misses or a stray crossing, often from typing, brightness or rushing. Try again in better conditions.
• Possible red-green deficiency: three or more of the eight red-green plates missed, or two plus a red-green arrangement. This is common — see an optician to confirm the type.
• Possible blue-yellow deficiency: two or more of the three blue-yellow plates missed, or one plus a tritan-type arrangement. This is rare and can be acquired, so get your eyes examined.
• Inconclusive: the demonstration plate was missed, so the screen or the answers are not reliable.

Getting a reliable screen

Colour filters, night modes and warm “eye comfort” settings shift every colour on screen and can make anyone fail the blue-yellow plates. OLED phones at low brightness, cheap laptop panels viewed at an angle, and projectors are the least reliable. If you want to see how colours look to people with each type of deficiency, try the colour blindness simulator; for designers, the contrast checker helps make text readable for everyone. The eye test chart is a separate screening for sharpness of vision.