Published by ColorVision Editorial Team. This educational content is not individual medical advice. Read our editorial policy and test methodology.
Quick answer
The most common colour-vision differences involve red and green; blue-yellow differences and complete colour-vision loss are less common. The exact type cannot be confirmed from a browser activity alone.
When to seek care: Seek an eye-care assessment for a new or worsening change in colour vision, or when a formal result is needed for work, study, or licensing.
Types of Colour Blindness
Colour blindness is not a single condition — it encompasses several distinct types of colour vision deficiency (CVD), each caused by different abnormalities in the cone cells of the retina. Understanding the different types is important for accurate diagnosis, workplace accommodations, and designing accessible content.
The Two Main Categories
All forms of colour blindness fall into two broad categories:
- Congenital (inherited) — present from birth, caused by genetic mutations
- Acquired — developed later in life due to disease, injury, or medication
Within congenital CVD, there are three primary axes of deficiency based on which cone type is affected:
- Protan (L-cone / red-sensitive)
- Deutan (M-cone / green-sensitive)
- Tritan (S-cone / blue-sensitive)
Red-Green Colour Blindness (Most Common)
Red-green CVD accounts for approximately 98% of all cases. It is caused by mutations on the X chromosome.
Protanopia
- Mechanism: Complete absence of L-cones (long-wavelength / red-sensitive)
- Prevalence: ~1% of males, under 0.01% of females
- What they see: Reds appear very dark or black; cannot distinguish red from green; reduced sensitivity to the red end of the spectrum
- Characteristic: The brightest point of the visible spectrum shifts toward yellow-green
Protanomaly
- Mechanism: L-cones present but with reduced or shifted sensitivity
- Prevalence: ~1% of males
- What they see: Similar to protanopia but less severe; reds appear muted or brownish
- Characteristic: Mild difficulty distinguishing red, orange, and green
Deuteranopia
- Mechanism: Complete absence of M-cones (medium-wavelength / green-sensitive)
- Prevalence: ~1% of males, under 0.01% of females
- What they see: Similar to protanopia — confuses reds and greens — but without the reduced brightness of reds
- Characteristic: Most common form of severe red-green CVD
Deuteranomaly
- Mechanism: M-cones present but with shifted peak sensitivity
- Prevalence: ~5% of males — the single most common form of colour blindness
- What they see: Greens shifted toward red; difficulty distinguishing green from red, yellow from orange
- Characteristic: Severity varies widely — some people have very mild anomalous trichromacy
Blue-Yellow Colour Blindness
Far rarer than red-green CVD, blue-yellow deficiencies affect the S-cones and are autosomal (carried on chromosome 7, not the X chromosome), meaning they affect men and women equally.
Tritanopia
- Mechanism: Complete absence of S-cones (short-wavelength / blue-sensitive)
- Prevalence: ~0.008% of the population (equally in men and women)
- What they see: Blue appears as green; yellow appears as violet or light grey; confusion between blue and green, and between yellow and red
- Characteristic: Often acquired rather than congenital
Tritanomaly
- Mechanism: S-cones present but with reduced sensitivity
- Prevalence: Extremely rare
- What they see: Similar to tritanopia but milder
- Characteristic: Often progressive if acquired
Complete Colour Blindness
Achromatopsia (Monochromacy)
- Mechanism: Complete absence of cone function — only rod vision remains
- Prevalence: ~1 in 30,000 people worldwide (no sex preference)
- What they see: Only shades of grey — truly black-and-white vision
- Associated symptoms: Severe light sensitivity (photophobia), reduced visual acuity (~20/200), involuntary eye movement (nystagmus)
- Note: Most “colour blind” people are NOT achromatopes — true monochromacy is extremely rare
Blue Cone Monochromacy
- Mechanism: Both L-cones and M-cones are non-functional; only S-cones and rods work
- Prevalence: ~1 in 100,000 males
- What they see: Very limited colour perception; primarily sees shades of blue with some grey
- X-linked: Like red-green CVD, primarily affects males
Comparing the Types at a Glance
| Type | Cone Affected | Prevalence (Males) | Severity | Can be Corrected? |
|---|---|---|---|---|
| Deuteranomaly | M-cone (shifted) | ~5% | Mild–Moderate | Partially with filters |
| Deuteranopia | M-cone (absent) | ~1% | Moderate–Severe | Partially with filters |
| Protanomaly | L-cone (shifted) | ~1% | Mild–Moderate | Partially with filters |
| Protanopia | L-cone (absent) | ~1% | Moderate–Severe | Partially with filters |
| Tritanopia | S-cone (absent) | ~0.01% | Moderate | No |
| Achromatopsia | All cones | ~0.01% | Complete | No |
How to Find Out Which Type You Have
Browser activities like the digit plate screen and hue arrangement practice can show how you responded to a colour task on one device. They cannot establish whether you have a colour-vision deficiency or determine its type. Clinical tools such as an anomaloscope may be used by a professional for controlled classification.
ColorVision’s digit plate activity uses original browser-generated plates and intentionally does not report a protan or deutan diagnosis.
Frequently Asked Questions
Can you have more than one type of colour blindness? In rare cases, yes — a person can be affected by both red-green and blue-yellow deficiencies simultaneously. This is most common with acquired CVD caused by disease.
Is the most common form of colour blindness severe? No. Deuteranomaly (the most common type) is often quite mild. Many people with deuteranomaly are not even aware they have it until they are tested.
Can colour blindness be inherited from a grandfather? Yes — this is the classic inheritance pattern. A grandfather passes his X-linked CVD gene to his daughters, who become carriers, and then 50% of their sons inherit the condition.
Evidence & sources
These sources provide background on colour vision deficiency and conventional clinical testing. ColorVision’s browser-based activities are educational screens, not clinical instruments.
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