How to Check a Design for Color Blindness
Updated 2026-06-21
To check a design for color blindness, take a screenshot of your UI or chart, drop it into a color-vision simulator, and switch between protanopia, deuteranopia, and tritanopia to see whether any meaning carried only by color disappears. Roughly 1 in 12 men has some form of color-vision deficiency, so this is one of the fastest accessibility checks you can run.
The Color-Blindness Simulator does exactly this in your browser. Your image is processed on a canvas locally and never uploaded — useful for unreleased product screenshots.
What the simulation modes mean
The tool applies published color-vision transform matrices to every pixel, so you see a realistic preview rather than a guess. The four modes cover the common cases:
- Protanopia (no red) — red appears dark and muddy; red/green pairs collapse.
- Deuteranopia (no green) — the most common type; red and green look nearly identical.
- Tritanopia (no blue) — blue and yellow become hard to tell apart.
- Achromatopsia (no color) — full grayscale, the harshest test of whether your design works on luminance alone.
Deuteranopia and protanopia together account for the large majority of cases, so if your design survives those two, you have covered most of your audience.
Step-by-step
- Capture a screenshot of the screen you want to test — a dashboard, form, chart, status badges, or a map legend.
- Open the Color-Blindness Simulator and drop the image onto the drop zone, or click to browse.
- Pick a type of color blindness from the selector. The tool renders a before/after compare slider.
- Drag the slider handle back and forth between Normal and the simulated view. Watch for anything that becomes invisible or ambiguous.
- Repeat for each mode. Achromatopsia last — if it still reads clearly in pure grayscale, your contrast is solid.
What to look for and how to fix it
The core question is simple: does any information rely on color alone? Common failures show up immediately in the slider.
- Charts and graphs — two lines or pie slices that were distinct now look the same. Fix with different line styles, direct labels, or patterns.
- Status indicators — a red "error" and green "success" dot become twins under deuteranopia. Add an icon (x versus check) or a text label.
- Form validation — a field outlined only in red gives no signal. Add an error message and an icon.
- Links — body-colored links that differ from text only by hue can vanish. Underline them.
The rule of thumb: never use color as the only way to convey meaning. Pair it with a shape, label, pattern, or position. If a state survives every simulation mode, it has a non-color cue doing real work.
Because everything runs on a canvas in your browser, you can test confidential mockups and internal tools without sending a single pixel to a server. Test your screen now with the Color-Blindness Simulator and ship a design everyone can read.