Color Contrast Checker MCP for AI. Verify Readability Against WCAG Standards.
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Color Contrast Checker instantly verifies if your text is readable on any background. Instead of guessing accessibility compliance, this MCP uses the official WCAG 2.1 formula to calculate the exact contrast ratio between two colors.
It tells you immediately if it meets AA or AAA standards for both normal and large text.
What your AI can do
Check color contrast
Pass foreground and background colors to get the exact contrast ratio, along with AA/AAA pass/fail status for normal and large text.
It determines the exact ratio between two specified colors down to two decimal places.
The MCP verifies if the color combination passes both AA and AAA standards set by the Web Content Accessibility Guidelines (WCAG).
You check for minimum contrast required when using standard body copy.
It verifies the necessary contrast level specifically for larger font sizes, which often has lower requirements than normal text.
The tool accepts input using HEX, RGB, HSL, or standard CSS color names.
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Color Contrast Checker: One Tool
This single tool calculates and verifies color contrast ratios, ensuring your UI meets critical web accessibility standards.
Make your AI actually useful.
Add this MCP to Claude, Cursor, or Windsurf and your AI stops guessing. It gets real tools to look things up, take action, and handle the stuff you keep doing by hand.
Start using Color Contrast Checker on VinkiusCheck Color Contrast
Pass foreground and background colors to get the exact contrast ratio, along with AA/AAA pass/fail status for normal and large text.
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Claude AI
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Works with Claude, ChatGPT, Cursor, and more
The Model Context Protocol standardizes how applications expose capabilities to LLMs. Instead of operating in isolation, your AI gains direct access to external platforms, live data, and real-world actions through secure, standardized connections.
This connection provides 1 powerful capabilities that interface natively with Claude, ChatGPT, Cursor, and other compatible AI platforms. No middleware. No custom integration required.
The Headache of Manual Accessibility Audits
Right now, checking color contrast feels like an educated guess. You open a spreadsheet or jump between tabs, manually plugging colors into different online tools, hoping they all use the same WCAG formula. If your team uses three different design systems, you spend hours cross-referencing ratios and converting hex codes just to prove that text is legible.
With this MCP, you simply feed in the two colors—the foreground and background—and your agent handles the rest. It runs the official calculations and spits out a definitive verdict: Pass or Fail for AA/AAA standards. The process goes from manual hours to an instant confirmation.
Color Contrast Checker MCP: Get Objective Compliance Data
The most tedious part of this process is the constant context switching. You have to remember if you're checking for normal text (4.5:1) or large text (3:1), and whether the tool accepts HSL or HEX values. This scattershot approach slows down iteration.
Now, your agent handles all that complexity internally using `check_color_contrast`. You just state the colors you're testing, and the MCP delivers a complete compliance report for every scenario in one shot. It makes accessibility data reliable.
What your AI can actually do with this
Your AI client needs to know if a color combination will pass an audit—and simple visual checks aren't enough. This MCP calculates the precise contrast ratio using the official WCAG 2.1 relative luminance formula, so you get math that works every time. You can feed it HEX, RGB, or HSL values and instantly check against standards for both normal body text and large headings.
It doesn't just spit out a number; it gives you a human verdict like 'Excellent (AAA)' or 'Fail.' Connecting this MCP via Vinkius means your agent can run these checks right alongside other development tasks, making sure every design choice is accessible before a single line of code ships.
019e387b-3056-7331-8b0b-823c5ea90236 
Here's how it actually works
The bottom line is you get an objective, auditable score that tells you exactly if your colors are accessible to everyone.
You send the MCP a foreground color and a background color, specifying their formats (e.g., #ffffff on #2563eb).
The engine runs those colors through the official WCAG 2.1 formula to calculate the ratio for normal and large text.
Your agent receives a simple report with the exact contrast number, pass/fail status for AA/AAA, and a clear verdict.
Who is this actually for?
Any developer or designer responsible for user-facing interfaces. This MCP helps the QA engineer who needs to prove compliance before a deadline, and the UX writer who just wants to make sure their subtle gray text isn't unusable.
They use this when implementing new components and need immediate confirmation that the chosen color palette meets accessibility standards.
They run checks against their mockups to ensure subtle label colors or background gradients don't create readability problems for users with low vision.
They use it during final audits, generating specific pass/fail evidence needed for client sign-off on WCAG compliance.
What Changes When You Connect
Eliminate guesswork on color choices. You get the precise ratio and compliance status for every combination you check, so your designs pass audits right out of the gate.
Check standards in one go. With check_color_contrast, you audit both normal text (4.5:1 / 3:1) and large text (7:1 / 4.5:1) requirements simultaneously. No more checking two different rulesets.
Work with any color format. Whether your source file uses HEX, RGB, or names, this MCP handles it. It's flexible enough for design systems that switch between color models.
Clearer results mean less friction. Instead of a table of numbers you have to interpret, the tool gives a simple 'Excellent (AAA)' verdict, making reporting straightforward.
Build compliance into your workflow. By connecting this MCP through Vinkius, your agent can automatically validate design tokens as they are defined in code or documentation.
See it in action
Audit a dark mode theme
A developer is building a dark mode UI. They ask their agent to check the white text (#ffffff) on the dark blue background (#1a1a2e). The MCP runs check_color_contrast and confirms it hits 13.2:1, passing AAA standards with flying colors.
Review subtle error messages
A UX designer needs a pale gray for disabled fields. They run the agent to check light gray text (#e2e8f0) on a white background (#ffffff). The MCP returns 1.67:1, immediately flagging it as 'Fail' and forcing them to choose a darker color.
Validate marketing assets
A content team uploads an image mockup for a campaign banner. They ask their agent to check the text color on the brand background. The MCP quickly calculates the ratio, ensuring the high-contrast requirements are met before printing or deploying.
Verify legal document standards
A compliance officer needs proof that all headings meet AAA contrast minimums. They use their agent to run check_color_contrast repeatedly across different sections of the template, providing an auditable report for legal review.
The honest tradeoffs
Relying on visual inspection
The designer just 'looks' at the hex code and thinks it looks dark enough against the background. The resulting contrast ratio is 1.5:1, which fails all standards.
Use check_color_contrast. Feed in both colors and let the MCP calculate the precise ratio. It will give you an objective fail/pass status so you don't rely on your eyes.
Ignoring large text requirements
The development team optimizes for normal body text (passing AA), but forget that certain headings are always viewed by users who need larger text sizes.
Always run check_color_contrast and ensure you check the 'Large Text' compliance status. The MCP handles both requirements in a single call.
Using generic online calculators
The team uses an outdated or generalized web tool that only supports basic HEX inputs, forcing them to manually convert RGB values elsewhere.
Use this MCP. It accepts multiple color formats (HEX, RGB, HSL) and is built on the official WCAG 2.1 standard, so you're always using the right math.
When It Fits, When It Doesn't
Use this MCP if your primary concern is objective, auditable text readability against established web standards like WCAG 2.1. Specifically, use it when you need to compare two colors and know if that pair will work for normal or large body copy. Don't use it if you are trying to determine the best color—it only checks compliance on colors you give it. If your goal is broader UI feedback (like checking font pairings or layout balance), you might need a different, multi-tool design auditing suite instead.
Questions you might have
Does Color Contrast Checker MCP handle all color formats? +
Yes. The tool accepts HEX, RGB, HSL, and standard CSS named colors, so you don't have to worry about converting inputs before running the check.
Can I use check_color_contrast for logos? +
While it will calculate the ratio, this MCP is designed for text legibility. If your logo requires a specific color contrast that fails WCAG standards, this tool will flag it.
How does check_color_contrast know which standard to use? +
The tool uses the official WCAG 2.1 relative luminance formula, checking both AA and AAA compliance levels for you automatically.
What is the difference between normal text and large text in check_color_contrast? +
Normal text checks require a higher minimum contrast ratio (e.g., 4.5:1) than large text does (e.g., 3:1). The MCP runs both checks so you know which standard applies to your specific element.
If I run check_color_contrast with an invalid color code format, what error response should I expect? +
The tool will return a clear validation error message. It expects standard formats like HEX or RGB; any input outside those structures will generate a specific failure notice, preventing calculation attempts.
Can check_color_contrast calculate contrast when one color is transparent or part of a gradient? +
No, the tool requires two solid, defined colors for comparison. It uses the WCAG luminance formula between specific inputs. For gradients, you must sample multiple points to get an accurate range.
Are there any rate limits or performance concerns when using check_color_contrast frequently? +
The MCP is built for high throughput and doesn't impose internal user-side rate limits. However, making excessive calls in a very short window might trigger standard platform throttling mechanisms.
Does check_color_contrast only adhere to WCAG 2.1 standards, or can it check older versions? +
It exclusively uses the official WCAG 2.1 standard and its specific mathematical formula for all calculations. This guarantees adherence to current W3C guidelines for accurate compliance.
My AI says this color combination passes WCAG. Should I trust it? +
No. LLMs cannot reliably calculate relative luminance — they approximate. This engine uses the exact W3C formula: L = 0.2126R + 0.7152G + 0.0722*B with sRGB gamma correction. Trust the math, not the prediction.
What's the difference between AA and AAA levels? +
AA requires 4.5:1 contrast for normal text — the legal minimum in most countries. AAA requires 7:1 — the gold standard for maximum readability. Large text (18pt+) has relaxed thresholds: 3:1 for AA, 4.5:1 for AAA.
Can I mix color formats? Like HEX for foreground and a CSS name for background? +
Absolutely. Pass '#333333' as foreground and 'white' as background, or 'rgb(0,0,0)' with 'hsl(0,0%,95%)' — the engine normalizes everything internally.
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