Free Color Blindness Simulator Online

Color Blindness Simulator: Preview Your Colors Under Color Vision Deficiency

A color blindness simulator shows you an approximation of how a set of colors shifts for someone with a color vision deficiency, so you can catch a problem pairing — two swatches that read as nearly identical to a colorblind viewer — before it ships in a chart, a UI, or a set of brand assets. Pick up to eight test colors, and the tool renders each one under protanopia, deuteranopia, tritanopia, and achromatopsia side by side with the original, so the comparison is immediate rather than something you have to imagine.

One thing to be direct about up front: this is a simulation built on standard, widely used approximation matrices, not a diagnostic tool and not a substitute for testing with actual colorblind users. Real color vision deficiency varies from person to person in both type and severity, and no fixed mathematical transform captures every individual's experience exactly. Treat the output here as a fast, practical way to flag likely problem colors during design — not as a medical assessment of anyone's vision.

How the Color Blindness Simulator Works

The tool is built around a row of editable swatches and a stack of simulated previews underneath:

• Choose your test colors. Five color swatches are preloaded by default, and each one opens your browser's native color picker when clicked. Add up to three more with the plus button, for a maximum of eight colors tested at once — enough to check a full chart legend or a small UI palette in one pass.
• Read the "Normal Vision" row. The first row always shows your colors exactly as entered, unmodified, so you have a fixed reference point to compare every simulated row against.
• Compare each simulated row. Below the reference row, four more rows show the same colors transformed for protanopia, deuteranopia, tritanopia, and achromatopsia in turn. Because every row uses the same swatch order, spotting which colors collapse into each other under a given condition is a matter of scanning down a column, not hunting across separate screens.
• Look for swatches that flatten together. The real signal isn't any single simulated color — it's when two colors that look clearly different in the "Normal Vision" row become hard to tell apart in a simulated row underneath. That's the pairing worth reconsidering in your actual design.

Everything updates the instant you change a swatch, so testing a red/green pairing against a blue/orange alternative is a matter of a few clicks, not a re-export from a design file.

Why Check Colors for Color Vision Deficiency

Color vision deficiency shows up often enough in the general population that it's worth checking early rather than after a design has already shipped. A few concrete situations where this matters:

• Chart and dashboard legends. A line chart that distinguishes series purely by red versus green, or a status indicator that relies on a red/green pairing alone, can become unreadable for a meaningful share of viewers. Running the exact colors from a chart's palette through the simulator surfaces this before the chart goes live.
• Status and alert colors in software. "Green means success, red means error" is a near-universal UI convention, and it's also one of the most common failure points for red-green color vision deficiency specifically. Pairing the color with an icon, label, or shape difference is the usual fix once a clash shows up here.
• Brand and marketing palettes. A logo or campaign built around two colors that are meant to contrast should still read as two distinct colors under simulation, especially if the design will appear in print, signage, or anywhere a viewer can't adjust settings to compensate.
• Wayfinding and map-based interfaces. Route colors, zone highlighting, and category shading on a map depend entirely on color separation to convey meaning — if two routes collapse into the same simulated shade, the map has failed at its one job for some viewers.
• Data visualization for a general audience. Any chart published where you don't control who's viewing it — a public report, a shared spreadsheet, an embedded widget — benefits from a palette that survives all three dichromacy types, not just looking good under normal vision.

Technical Deep Dive: How the Simulation Works

Protanopia, deuteranopia, and tritanopia are each a form of dichromacy — the complete absence of one of the three types of cone cells the eye normally uses to distinguish color, rather than a partial reduction. Protanopia is the absence of red-sensing cones, deuteranopia the absence of green-sensing cones, and tritanopia the absence of blue-sensing cones. Achromatopsia is a separate, much rarer condition involving no functional color cones at all, producing a fully grayscale view of the world.

To simulate each dichromacy type, this tool applies a fixed 3x3 matrix to a color's red, green, and blue channel values — the same widely cited style of transformation matrix used by common browser-based color blindness simulators. Each matrix redistributes the missing channel's contribution across the two remaining channels, approximating what a dichromat's eye would perceive from the same light. Achromatopsia is simulated differently: rather than a matrix, it converts a color to grayscale using a standard luma formula that weights green most heavily and blue least — the same general approach most everyday "convert to grayscale" image operations use, applied here to a single color instead of a full image.

A detail worth being precise about: the three dichromacy matrices here are applied directly to standard sRGB channel values without first linearizing them through a gamma curve — a deliberate, simpler approach than a full physiologically-modeled simulation would use, and consistent with how many popular browser-based simulators handle the same calculation. It produces a reasonable approximation for spotting problem color pairs, not a scientifically exact rendering of dichromat perception.

Some honest tradeoffs of this approach:

Aspect	What this simulator does	What it doesn't do
Coverage	Protanopia, deuteranopia, tritanopia, achromatopsia	Doesn't model every rare variant of color vision deficiency
Severity	Simulates full dichromacy (complete absence of one cone type)	Doesn't capture the graded severity range seen in real anomalous trichromacy without further approximation
Input	Individual hex colors you choose	Doesn't simulate a full photo or screenshot in this tool
Precision	Fast, consistent, good for comparing color pairs	Not validated against any individual's actual clinical vision test

Simulator vs Other Ways to Check Color Accessibility

This isn't the only way to check a palette against color vision deficiency, and each alternative has a different tradeoff:

• Other browser-based simulators. Several long-running web tools do something similar, often built around the same family of simulation matrices. Results across them tend to be broadly comparable since the underlying math is similar; differences usually come down to interface and how many colors you can compare at once.
• Image-editing software with a built-in vision-deficiency proof mode. Photoshop and similar tools can preview an entire open image under a simulated color vision deficiency, which is useful when the concern is a photo or a finished mockup rather than a handful of individual colors.
• Browser developer tools with a vision-deficiency emulation mode. Some browsers can render an entire live web page as if viewed with a specific color vision deficiency, which catches real rendered contrast issues (including ones from images, gradients, and overlapping elements) that a color-only simulator like this one won't reproduce.
• Testing with actual colorblind users. Nothing above replaces feedback from real people with the condition in question — simulations are a fast filter for catching obvious problems early, not a final accessibility sign-off.

Used together, a quick check here during color selection followed by a full-page emulation pass later in development covers more ground than either step alone.

How This Tool Handles Your Colors

Every color you pick or type stays local to your browser session — the tool works entirely on hex values you enter yourself, with no image or file involved and nothing sent anywhere to be processed. Closing the tab discards whatever colors you were testing, and nothing about the session is stored or tied to an account.

If you need to run this simulation from a script or a design pipeline rather than the browser interface — checking a whole palette programmatically before a build, for instance — the same simulation logic is available as a metered API endpoint, documented at /docs. Worth noting: calling the API means sending the color value to our server for that one calculation, which is a different privacy shape than the fully local browser tool above; it's still just a hex string and a deficiency type, never an image. The API also covers three additional "anomaly" variants — protanomaly, deuteranomaly, and tritanomaly — which represent milder, partial forms of color vision deficiency rather than full dichromacy. Since there's no single fixed matrix for these graded conditions, the API approximates each one as a 50/50 blend between the original color and its full-dichromacy simulated counterpart; that blend is a deliberate simplification, documented as such, and isn't in the browser tool above.

Common Questions About Color Blindness Simulation

Is this simulator medically accurate enough to diagnose color blindness?

No — it's a design-checking approximation built on standard simulation matrices, not a diagnostic instrument. An actual diagnosis requires a clinical vision test administered by an eye care professional, and real color vision deficiency varies between individuals in ways a fixed matrix can't fully capture.

What's the practical difference between protanopia and deuteranopia?

Both fall under "red-green color blindness" and both make red and green hard to distinguish, but they arise from different missing cone types and shift colors slightly differently. In practice, both usually flag the same problem color pairs, so checking against both is a good habit even though the exact simulated shades differ.

Can this tool simulate a whole photo or screenshot, not just individual colors?

Not this particular tool — it works on the hex colors you enter directly, up to eight at a time, rather than processing an uploaded image pixel by pixel. For a full-image simulation, an image-editing program's built-in vision-deficiency preview mode is the better fit.

How many colors can I compare at once?

Up to eight. Five are loaded by default to get you started quickly, and you can add up to three more, which comfortably covers most chart legends and small UI palettes in a single pass.

Does the simulator account for how severe someone's color vision deficiency is?

The four core types simulate full dichromacy — complete absence of one cone type — rather than a spectrum of severity. The milder "anomaly" variants, available through the API, approximate reduced severity as a blend rather than a precisely graded model, and that's an intentional simplification rather than a claim of clinical precision.

What should I actually do once I spot two colors that look identical in a simulated row?

Swap one of the colors for something further apart in lightness as well as hue — lightness differences tend to survive dichromacy simulation better than hue differences alone — or add a non-color signal such as an icon, pattern, label, or shape so the distinction doesn't depend on color perception at all.

Related Color Accessibility Tools

Checking a palette for color vision deficiency is usually one step in a broader accessibility and color workflow. These tools cover the adjacent steps:

• Contrast Checker — verify that a text and background color pair meets WCAG contrast requirements, a separate but related accessibility check from color vision deficiency simulation.
• Color Palette Generator — generate an initial set of coordinated colors from a base hue, which you can then run through this simulator before committing to it.
• Color Shade & Tint Generator — produce lighter and darker variants of a color, useful for building the lightness separation that helps a palette survive dichromacy simulation.
• Color Converter — convert a flagged color between hex, RGB, HSL, and other notations to hand off to a developer or a design file.
• Tailwind CSS Color Finder — look up the closest named Tailwind utility class once you've swapped in a safer color after a simulation check, to keep a Tailwind-based project consistent.