When the Color Blindness Simulator seems to misbehave, the cause is usually one of two things: something stopped the tool from running, or it ran but the result is not usable. This guide starts with the fastest checks, then walks through the common problems and exact fixes.
Quick Checks First
- Refresh the page - a stalled session is the most common cause of nothing happening.
- Confirm the input is not empty and actually contains what you meant to submit.
- Try the smallest possible input; if that works, the issue is size, not the tool.
- Turn off browser extensions that block scripts, then reload and test again.
- Update or switch browsers if the problem repeats across sessions.
Common Problems and How to Fix Them
Two colours still look the same when simulated
Separate them by lightness, not just hue - luminance differences survive most deficiencies.
I fixed the palette and it lost the brand feel
Adjust just enough to separate the states - accents can stay expressive where meaning does not depend on them.
Only charts fail, everything else passes
Information carried by colour alone is the real issue - add labels, patterns or icons alongside.
Which deficiency should I test?
Red-green deficiencies cover the majority of cases - start there, then check the others.
The simulation looks unrealistic
Simulations approximate vision - treat them as a strong signal, not a medical guarantee.
Passing the simulator still got complaints
Pair simulation with real contrast ratios - both are required for genuinely readable design.
When It Works but the Output Is Poor
If the tool runs fine but the result misses, the problem is almost always the brief, not the software:
- Fixing colours without rechecking the original goal
- Assuming one deficiency type covers everyone
- Fixing hue but leaving lightness identical
- Testing only the happy-path palette
How to Stop It Happening Next Time
- Keep a saved prompt template for every task you repeat.
- Change one setting per generation so causes stay obvious.
- Run a two-minute sanity test with known input after any update.
- Note every failure and its fix; a short troubleshooting log pays for itself.
Still Stuck?
Reproduce the problem with the smallest possible input and note the exact steps that triggered it. A one-line description of what you did, what you expected and what happened is enough to get a precise answer from support or a colleague.
Frequently Asked Questions
What types of colour blindness exist?
Red-green forms are most common (deuteranopia and protanopia); blue-yellow (tritanopia) is rarer.
Does passing the simulator make my design accessible?
It is one essential check - combine it with contrast ratios and non-colour cues.
Can I simulate an image or only colours?
Both - test individual swatches or preview a whole graphic.
Is anything uploaded?
No - simulation runs entirely in your browser.
Related Guides
- How to Use Color Blindness Simulator
- What Is a Color Blindness Simulator and How Does It Work?
- Color Blindness Simulator Examples: Real Scenarios and Results
- Color Blindness Simulator for Designers and Front-end Developers
- Best Color Blindness Simulator Alternatives Worth Trying
- Color Blindness Simulator Tips and Best Practices
- Is Color Blindness Simulator Safe? Free vs Paid
- More color tools and guides