The Purple-Blue Color Blind Test is an interactive online tool that examines your ability to tell apart purple and blue hues. It generates 20 randomized Ishihara-style dot plates, each embedding numbers visible only if the colors can be separated. The difficulty adapts to your responses, making the next plate easier or harder depending on accuracy. After completing the test, you receive a full score report, difficulty analysis, and timing statistics.
Ishihara Blue–Purple Color Discrimination Test
This test evaluates your ability to distinguish subtle blue–purple hue differences using Ishihara-style adaptive plates.
Test Instructions
- Look at the circle and identify the number formed by the coloured dots (blue vs purple contrast)
- Type the number you see in the input field and click Submit
- If you cannot see a number, you can click Skip
- The test adapts to your ability — correct answers reduce the blue–purple hue gap
- Complete all 20 plates for a comprehensive assessment
- Ensure neutral lighting and disable any colour-enhancing or -adjusting features on your screen
- The test measures your response time for each plate (speed + accuracy contribute to interpretation)
Test Results
Features
- 20 Unique Plates: Each run presents 20 newly generated Ishihara-style circles.
- Adaptive Difficulty: Dynamic adjustment based on correct or missed answers.
- Seven Levels: From Very Easy to Extreme, altering hue distance and saturation contrast.
- Procedural Plate Generation: Every plate uses randomized dot fields, layouts, and shapes.
- Numeric Range: Embedded numbers between 1 and 99.
- Purple–Blue Focus: Specially tuned to evaluate perception across the violet–blue axis.
- Micro-Pattern Variants: Plates incorporate grids, blocks, and fine-grain textures.
- Timing Metrics: Response time logged per plate.
- Level-by-Level Tracking: Accuracy recorded at each difficulty tier.
- Extreme Escalation: Continuous hue reduction at the hardest setting.
- Live Score Counter: Tally updates as you progress.
- Progress Indicator: Visual bar showing completion percentage.
- Instant Feedback: Correct/Incorrect alerts after each response.
- Skip Function: Option to bypass a plate if no number is visible.
- Difficulty Display: Labels plus visual markers show your current level.
- Result Breakdown: Score, speed, and overall performance summary.
- Interpretation Text: Context for educational understanding of your outcome.
- Detailed Stats: Accuracy by level, including attempts and success rates.
- One-Click Restart: Reset and retake instantly.
- Mobile Ready: Responsive layout across phone, tablet, and desktop.
- Accessibility: Keyboard input and ARIA announcements for screen readers.
This tool is educational only — it cannot provide a medical diagnosis. If concerned about your results, consult an eye care professional.
Blue-green circle from the test with number 61
Results & Interpretation
After 20 plates you’ll see:
- Total score — number of correct identifications.
- Maximum difficulty reached — depth of hue discrimination.
- Mean response time — indicates response confidence.
How to interpret
- High accuracy at advanced levels suggests typical violet–blue vision.
- Difficulty even at early stages may indicate a tritan-type issue. This tool cannot diagnose; professional testing is required.
Results highlight patterns but are not medical evaluations.
How the Test Operates
Ishihara plates hide numbers within multicolored dot patterns. People with normal purple–blue vision perceive the numbers, while others may struggle. This test manipulates hue and saturation on the violet–blue spectrum to scale difficulty.
Limitations
- Display calibration, brightness, and environment affect accuracy.
- This is not equivalent to clinical threshold tests.
- Using tinted glasses or digital filters can distort results.
Calibration & Accessibility
- Disable Night Shift, True Tone, or color filter modes.
- Use the same device for consistent comparisons.
- Keyboard: enter numbers, press Enter to submit, or Skip if blank.
- Screen readers: each progress update is announced.
Frequently Asked Questions
What does this tool assess?
Your ability to distinguish purple from blue at varying difficulty levels.
Can it diagnose vision deficiency?
No. It is an awareness test only. Clinical tests are required for diagnosis.
Why do some plates appear blank?
As hue separation decreases, numbers become difficult or impossible to detect.
Is phone testing accurate?
It works, but a calibrated larger screen provides more reliable outcomes.
Can results be improved?
No practice can change inherent color vision. Neutral lighting and proper screen setup only improve fairness.
Sources and References
- Wikipedia: Tritanopia – Description of blue–yellow deficiencies.
- Barbur JL (2016) – Vision Research – Mechanisms of color discrimination.
- Neitz & Neitz (2019) – Frontiers in Neuroscience – Genetics and physiology of color vision.
- Mantiuk et al. (2018) – Investigative Ophthalmology & Visual Science – Limits of color discrimination on digital displays.
- Horiguchi et al. (2022) – Scientific Reports – Neural responses in color vision testing.
Did this test highlight any differences in your purple–blue vision? Would you like more features? Share feedback below.
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