# ColorBlindTests.net — Full Site Documentation for LLMs

> ColorBlindTests.net provides free, clinically-informed online color blind tests. All tests run in-browser with instant results. No signup or payment required.

## Site Overview

ColorBlindTests.net helps people screen for color vision deficiency (CVD) using established ophthalmological methods. The site covers:
- Interactive screening tests (Ishihara plates, specialized red-green/blue-yellow tests, Farnsworth-Munsell 100 Hue)
- Educational content about color blindness types, genetics, prevalence, and daily life impact
- Practical guides for driving, careers, parenting, and accommodations

### Key Facts
- Color blindness affects ~8% of males and ~0.5% of females worldwide (~300 million people)
- Most common type: Deuteranomaly (green-weak), affecting ~5% of males
- Red-green CVD is X-linked recessive; blue-yellow CVD is autosomal dominant
- Color blindness is not curable but manageable with awareness and accommodations

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## Tests

### Ishihara Color Blind Test
URL: https://colorblindtests.net/ishihara-test
- Method: Ishihara pseudoisochromatic plates (developed 1917 by Dr. Shinobu Ishihara)
- Plates: Up to 38 plates with hidden numbers in colored dot patterns
- Detects: Red-green color blindness (Protanopia, Deuteranopia, Protanomaly, Deuteranomaly)
- Accuracy: ~95% screening accuracy under proper lighting
- Duration: 2-3 minutes
- Best for: Initial screening for adults and children age 5+

### Red-Green Color Blind Test
URL: https://colorblindtests.net/red-green-color-blind-test
- Specialized screening for Protanopia (red-blind) and Deuteranopia (green-blind)
- Tests the L-cone (OPN1LW gene) and M-cone (OPN1MW gene) pathways
- Most relevant test for the ~7% of males with red-green CVD

### Blue-Yellow Color Blind Test
URL: https://colorblindtests.net/blue-yellow-color-blind-test
- Screens for Tritanopia and Tritanomaly
- Tests the S-cone (OPN1SW gene on chromosome 7) pathway
- Tritanopia is autosomal dominant (affects males and females equally)
- Very rare: <0.01% of population

### Kids Color Blind Test
URL: https://colorblindtests.net/kids-color-blind-test
- Designed for children who can identify basic shapes and numbers
- Simplified interface suitable for ages 4-12
- Uses age-appropriate instructions

### Cambridge Color Test
URL: https://colorblindtests.net/cambridge-color-test
- Method: Landolt C rings embedded in pseudoisochromatic (random luminance) noise
- 12 plates; the gap direction of each C must be identified
- Screens both red-green and blue-yellow color vision deficiency
- Online adaptation of the clinical Cambridge Colour Test
- Duration: 3-5 minutes; instant results

### Farnsworth D-15 Test (Clinical Guide)
URL: https://colorblindtests.net/farnsworth-d-15-test
- Method: 15-cap dichotomous arrangement test (plus one fixed reference cap), original Dean Farnsworth 1947 design
- Computes total error score, per-axis (protan/deutan/tritan) error counts, and a diagnostic label
- Scoring based on the Vingrys & King-Smith method (Confusion Angle + Confusion Index, IOVS 1988)
- Saturated and Lanthony desaturated modes; lighting calibration check before the test
- Severity thresholds: <100 normal/very mild, 100-700 mild, 700-1100 moderate, >=1100 severe
- Occupational pass/fail standards covered: US police (0-1 major crossing), FBI (backup after Ishihara), US Military (varies by MOS), Canadian Armed Forces, FAA (no longer accepted as of January 2025 — CAD and Waggoner CCVT are approved alternatives), maritime/STCW
- Reported sensitivity ~53-80%, specificity ~97-100% vs anomaloscope
- Important: screening tool, not a medical diagnosis; online results are not valid for official medical certification

### D-15 Color Blind Test (Quick)
URL: https://colorblindtests.net/d15-color-blind-test
- Streamlined 15-cap arrangement test for fast classification of CVD type and severity
- Plots cap order to reveal protan, deutan, or tritan confusion axis

### Farnsworth-Munsell 100 Hue Test
URL: https://colorblindtests.net/farnsworth-munsell-100-hue-test
- Comprehensive color discrimination assessment
- Tests ability to arrange colors in correct hue order
- Identifies specific color confusion axes
- Distinguishes between protan, deutan, and tritan defects
- Produces a numeric Total Error Score (TES); more detailed than Ishihara — determines severity level

### Farnsworth Lantern Test (FALANT)
URL: https://colorblindtests.net/lantern-test
- Method: Paired signal lights (red, green, white) shown for 2 seconds each
- Developed by Commander Dean Farnsworth in 1954 at the Naval Submarine Medical Research Laboratory
- Standard test for U.S. Navy, Coast Guard, FAA, and merchant marine services
- 9 light pairs testing all combinations of red, green, and white
- Designed to pass individuals with mild CVD who can safely identify navigation signals
- ~30% of Ishihara failures can pass the FALANT
- Online version uses yellow as screen substitute for white
- Important: not a replacement for clinical FALANT certification

### Color Blindness Simulator
URL: https://colorblindtests.net/color-blindness-simulator
- Upload any image to preview how it looks with different types of color vision deficiency
- Simulates protanopia, deuteranopia, tritanopia, and achromatopsia (full color blindness)
- Useful for designers checking color accessibility and for people explaining their vision to others
- Runs entirely in-browser; uploaded images are not stored

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## Blog Articles

### Best Jobs for Colorblind People (and Careers to Avoid)
URL: https://colorblindtests.net/blog/jobs-for-colorblind-people
Topics covered:
- Careers requiring color vision tests: commercial aviation (FAA 14 CFR Part 67), electrical work (NEC wire codes), rail/commercial driving (FRA), firefighting (NFPA), military (CP-1/2/3 tiers)
- Unrestricted careers: software engineering, law, finance, writing, data analysis, teaching, HR
- Gray area careers: graphic design, photography, medicine, culinary arts
- Workplace statistics: 75% of colorblind workers report slowdowns, 58% of accommodations cost nothing (EnChroma/BusinessWire 2021 survey, n=810)
- ADA protections and disclosure guidance

### Can Colorblind People Drive? License Rules in 20+ Countries
URL: https://colorblindtests.net/blog/driving-with-color-blindness
Topics covered:
- Traffic light design for accessibility: position-based (MUTCD standards), brightness differences, shape innovations (Canada)
- No restrictions: US, UK, EU, Australia, New Zealand, Canada, South Africa
- Testing required: Singapore, Malaysia, India, Thailand, Romania, Indonesia
- Banned/restricted: China (since 1996), Russia (since 2012), Turkey
- Commercial vs private license differences
- Safety data: no peer-reviewed evidence of higher accident rates (Heliyon 2023 review)
- 5 practical tips for colorblind drivers

### The Genetics of Color Blindness: Why 1 in 12 Men Are Affected
URL: https://colorblindtests.net/blog/genetics-of-color-blindness
Topics covered:
- Cone cells and opsins: L-cones (564nm, OPN1LW), M-cones (534nm, OPN1MW), S-cones (420nm, OPN1SW)
- X chromosome connection: OPN1LW and OPN1MW at Xq28, 98% DNA sequence similarity
- Why males are 16x more affected than females
- Four types of red-green CVD with prevalence: Deuteranomaly (~5%), Protanomaly (~1.3%), Deuteranopia (~1.2%), Protanopia (~1%)
- Inheritance scenarios with probabilities for each parent combination
- Why color blindness "skips" a generation (X-linked recessive pattern)
- Acquired vs genetic color blindness
- Gene therapy research: Mancuso et al. 2009 (Nature), current clinical trials

### Is My Child Color Blind? Age-by-Age Signs Parents Should Know
URL: https://colorblindtests.net/blog/early-signs-child-color-blindness
Topics covered:
- Ages 2-3: sorting game failures, wrong fruit identification, unusual crayon preferences
- Ages 4-5: color-by-number confusion pairs (red/green, red/brown, orange/green, purple/blue), "learning delay" misdiagnosis
- Ages 6-8: academic impact (color-coded worksheets, sports confusion), social/emotional effects
- Available tests by age: CVTME (age 4+), HRR plates, Ishihara (age 5-6+)
- Common parent mistakes: "sees in black and white", drilling colors, dismissing girls
- School accommodation guidance (Section 504, IEP considerations)
- Prevalence by ethnicity: Northern European 8%, East Asian 5%, African 4%, Indigenous Australian 2%
- Screen-based learning challenges and OS color filter settings

### Types of Color Blindness: A Complete Reference
URL: https://colorblindtests.net/blog/types-of-color-blindness
Topics covered:
- The three categories: anomalous trichromacy (color-weak), dichromacy (one cone missing), monochromacy (achromatopsia)
- Red-green types (protanopia, protanomaly, deuteranopia, deuteranomaly) and blue-yellow types (tritanopia, tritanomaly)
- What each type confuses and how everyday colors appear
- Prevalence and inheritance for every type

### How Color Blind Glasses Work
URL: https://colorblindtests.net/blog/how-color-blind-glasses-work
Topics covered:
- The optical principle: notch filters that cut overlap between L- and M-cone sensitivity
- What EnChroma/Pilestone-style glasses can and cannot do (they do not cure or restore missing cones)
- Indoor vs outdoor performance, and why they don't help dichromats as much as anomalous trichromats
- What the research actually shows about color discrimination improvement

### Army & Military Color Blind Requirements
URL: https://colorblindtests.net/blog/army-color-blind-requirements
Topics covered:
- Color vision testing in enlistment (Ishihara, FALANT) and the CP-2/CP-3 classification tiers
- Which MOS/specialties require normal color vision (aviation, electronics, ammunition)
- Branch-by-branch differences (Army, Navy, Air Force, Marines, Coast Guard)
- Waiver and retest options

### How to Pass the Farnsworth D-15 Test
URL: https://colorblindtests.net/blog/how-to-pass-farnsworth-d-15-test
Topics covered:
- What the D-15 actually measures and what counts as a pass (major crossings vs adjacent swaps)
- Whether practice changes results (2018 PubMed study: mixed, some luminance-cue compensation)
- Lighting and screen conditions that affect outcomes
- Honest framing: the test reflects underlying color vision, not learned strategy

### Farnsworth D-15 vs Munsell 100 Hue
URL: https://colorblindtests.net/blog/farnsworth-d-15-vs-munsell-100-hue
Topics covered:
- Both are arrangement tests by Dean Farnsworth, but differ in caps, time, and sensitivity
- D-15: 15 caps, 2-3 min, pass/fail classification of moderate-to-severe defects
- 100 Hue: 85 caps, 15-20 min, granular Total Error Score for fine hue discrimination
- When clinicians use each, and where they sit in the diagnostic workflow

### Color Blindness FAQ
URL: https://colorblindtests.net/blog/color-blindness-faq
Topics covered:
- Common questions on diagnosis, prevalence, inheritance, curability, and daily-life impact
- Differences between screening tests and clinical diagnosis
- Whether color blindness can develop or worsen over time (congenital vs acquired)

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## Languages

All test pages and the homepage are fully localized into:
- English (default, no URL prefix) — https://colorblindtests.net/
- Simplified Chinese (zh) — https://colorblindtests.net/zh/
- Spanish (es) — https://colorblindtests.net/es/
- German (de) — https://colorblindtests.net/de/

Each localized page is independently indexable and declares hreflang alternates linking all language versions. The content (titles, instructions, clinical explanations, and FAQs) is fully translated, not machine-swapped UI chrome.

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## Color Blindness Types Reference

| Type | Affected Cone | Prevalence (Males) | Inheritance |
|------|--------------|-------------------|-------------|
| Deuteranomaly | M-cone (shifted) | ~5% | X-linked recessive |
| Protanomaly | L-cone (shifted) | ~1.3% | X-linked recessive |
| Deuteranopia | M-cone (absent) | ~1.2% | X-linked recessive |
| Protanopia | L-cone (absent) | ~1% | X-linked recessive |
| Tritanopia | S-cone (absent) | <0.01% | Autosomal dominant |
| Tritanomaly | S-cone (shifted) | Very rare | Autosomal dominant |
| Achromatopsia | All cones | 1 in 30,000 | Autosomal recessive |

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## About

ColorBlindTests.net is an independent health education resource. All tests are free, require no signup, and run entirely in the browser. Tests provide screening-level results and are not a substitute for clinical diagnosis by an eye care professional.

Website: https://colorblindtests.net