Hue Neighbor Discrimination
BLUE
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BLUE
OR
PURPLE?
A reference color is shown. Two test patches appear below it — one matches the reference, one is a slightly shifted hue. You pick which matches. As you answer correctly, the patches get closer together until you can no longer tell them apart. That gap is your threshold.
Why this test exists
The most common way people first discover a color vision difference is the blue/purple confusion. Something that looks clearly blue to one person looks purple or gray-blue to another. This test finds your just-noticeable difference across seven hue pairs — blue/purple first, then six others covering all three clinical color confusion axes.
How to take the test
Maximize brightness. Two patches will look very similar — brightness matters more here than in any other test on this site.
Low brightness compresses hue contrast and produces falsely wide thresholds.
Cover one eye with your palm. Both eyes tested separately.
Acquired color deficiencies are often asymmetric between eyes — this is the only test that catches that reliably.
A reference color is shown above two test patches. Tap the patch that matches the reference.
One patch matches the reference exactly. The other is a slightly different hue (or saturation). The gap between them narrows as you answer correctly.
When both test patches look completely identical, tap "Both look the same." That is the correct response — not a cop-out.
The test is designed to push you to that point. Guessing when you can't tell skews the threshold — using that button is what makes the result accurate.
Eye complete
LEFT
EYE
Genetic CVD is symmetric. Second eye only adds time, not data.
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Results
HUE
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HUE
THRESHOLD
PROFILE
Right eye
—
Left eye
—
Results Disclaimer
Results are educational screening estimates only. Hue discrimination on a consumer screen is constrained by sRGB gamut, display calibration, and ambient lighting. Thresholds measured here are screen-relative and differ from clinical colorimetric JND values. Do not use these results for clinical, employment, or medical decisions. Consult a licensed optometrist for definitive color vision assessment.