Trichrome: Color Blind Test · iOS 17+
Color blind test app with nine colour vision tests in one album
Trichrome is a colour vision test for iPhone that goes beyond one set of number plates: nine screening tests modelled on clinical methods, from Ishihara-type plates to a Farnsworth D-15 and a Cambridge-style gap ring. It suggests the likely type (protan, deutan or tritan) and degree. It is a screening tool, not a diagnosis.
Why one online plate test rarely gives a clear answer
- You missed a few numbers on an online Ishihara-style test and now wonder: is it red-green, how strong, or was it just the screen? A pass/fail plate set cannot say.
- Most free tests only look for red-green defects. Blue-yellow (tritan) deficiency is rare, but plain number plates are not designed to find it.
- Your child cannot read digits yet, so the usual number plates do not work, and you would like a rough idea before seeing an eye doctor.
- Friends ask "so what do you actually see?" and it is hard to explain without showing them.
How Trichrome checks colour vision from several angles
Number plates, free
Test I uses pseudo-isochromatic plates of the Ishihara type: a digit hidden in dots that a typical eye reads and a red-green deficient eye may miss. It is free and takes about two minutes.
Symbol plates for type and degree
Test II follows the HRR idea: circles, crosses and triangles at several strengths, including blue-yellow plates, so the result shows the likely type and degree, not just a pass or fail.
Shapes for kids
Test III uses large shapes instead of digits, for children who do not know numbers yet. It looks at both red-green and blue-yellow.
Arrangement tests: D-15, D-15d and 100 Hue
Put coloured caps in order by hue. The Farnsworth D-15 shows the type of defect by the direction of crossings, the pale Lanthony D-15d catches milder defects, and the 85-cap Farnsworth-Munsell 100 Hue in four trays gives a total error score (TES).
Gap ring, closest colour and signal lights
Test VII is modelled on the Cambridge Colour Test: find the gap in a ring of dots while adaptive staircases measure thresholds along the protan, deutan and tritan axes in CIE u′v′. Test VIII follows the City University test, and test IX the Farnsworth lantern with red, green and white lights.
Summary report and "See as"
Results from all tests are combined into a report with the likely type and degree that you can export as an image. "See as" shows the camera, a photo or a sample scene through a simulation of protanopia, deuteranopia or tritanopia with adjustable strength.
Free test and one-time unlock
Test I (number plates) is free. A one-time purchase of $0.99 unlocks the other eight tests, the summary report and the "See as" simulator forever. No subscription, no ads, no account. The purchase supports Family Sharing.
App StoreComing soon to the App StoreFrequently asked questions
Can an app tell me if I am color blind?
An app can screen for a likely colour vision deficiency, but it cannot diagnose one. Phone screens differ in colour and brightness, so treat the result as a reason to see an eye-care professional, who can test you with calibrated materials.
Is the Trichrome test the same as the Ishihara test?
No. Trichrome's number plates are of the Ishihara type, meaning they use the same principle of a digit hidden in coloured dots, but they are generated by the app and are not copies of the printed Ishihara book.
Can Trichrome detect tritanopia (blue-yellow color blindness)?
Several tests look at the blue-yellow axis: the symbol plates, the shapes for kids, the arrangement tests and the gap ring, which measures a tritan threshold. The free number plates are aimed at red-green only.
How do I get the most reliable result on a phone?
Before each test Trichrome asks you to turn screen brightness up, switch off Night Shift and True Tone, remove colour filters or tinted glasses, sit indoors out of direct sunlight and hold the phone at arm's length.
Can children take the test?
Yes, test III uses large shapes instead of digits for children who cannot read numbers yet. An adult should sit with the child, and any concern should be checked by a paediatric eye doctor.
What is the difference between protan, deutan and tritan?
They name which of the three cone types is missing or altered: protan affects the long-wavelength (red) cones, deutan the medium-wavelength (green) cones and tritan the short-wavelength (blue) cones. Deutan defects are the most common.
Does Trichrome collect my results?
No. Results are stored only on your iPhone and you can delete them in Settings. The app has no account, no analytics and no ads. The camera in "See as" is used only for a live preview and nothing is recorded.
How much does Trichrome cost?
The number plate test is free. Everything else, including the other eight tests, the report and the simulator, is a one-time $0.99 purchase with no subscription.
Guides and articles
Types of color blindness: protan, deutan and tritan explained
Color blindness comes in three main families named after the cone that is affected: protan (red cones), deutan (green cones) and tritan (blue cones). Red-green types, protan and deutan, affect about 8% of men and 0.5% of women of Northern European descent; deutan is the most common and tritan is rare.
Read →Ishihara vs D-15 vs Cambridge: which color blindness test tells you what
Ishihara plates are a fast red-green screen, HRR plates add blue-yellow and grade severity, the Farnsworth D-15 shows the type of defect, the 100 Hue measures fine discrimination, and the Cambridge Colour Test measures thresholds on the protan, deutan and tritan axes. No single test answers every question, so clinics often combine them.
Read →Color blindness test for kids: from what age and which test
Most children can do a colour vision test with shapes instead of numbers from about age 3 to 4: in one study, 75% of children over 3 and all children aged 4 or older could complete a shape-based test. A home check gives a first hint; an abnormal or uncertain result should be confirmed by a paediatric eye-care professional.
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