Color Similarity Calculator API

About the Color Similarity Calculator API

Color Similarity Calculator compares two hex colors and tells you how close they are. It works by converting hex colors to RGB and HSL, calculating Euclidean distance in color space, and comparing hue, saturation, and lightness differences. Send color1 and color2, with or without the # prefix, and get back both colors broken out into RGB and HSL, an overall similarity percentage, a plain-language rating from very different to nearly identical, and a flag that says whether the two values are the same color.

Designers use it to catch near-duplicate swatches in a palette, to check a brand color against what a product or print proof actually shows, and to group user-chosen colors that are close enough to treat as one.

The Free plan returns the overall score, the rating and the channel breakdowns. Paid plans add the measurements behind the score: RGB distance and RGB similarity, HSL similarity, a Delta E color difference computed in CIE-LAB, and the separate hue, saturation and lightness gaps, so you can set your own color matching threshold instead of relying on the rating.

How it works

Each color1 and color2 value has its # stripped and is read as hex. Three-digit shorthand is expanded (F00 becomes FF0000) and the alpha byte of an eight-digit value is dropped, so transparency never affects the result. The channels are converted to HSL in the usual way, with hue in degrees and saturation and lightness as percentages, rounded to one decimal in the response.

rgb_distance is the straight-line distance between the two colors in 0-255 RGB space, and rgb_similarity rescales it to a percentage of the largest possible distance (black to white). hsl_similarity is built from the hue gap, measured around the color wheel so 350 and 10 degrees are 20 apart, plus the saturation and lightness gaps, each normalised to 0-1 before they are combined. overall_similarity is the plain average of those two percentages. similarity_category maps it with fixed cut-offs: 95 and above is nearly identical, 85 very similar, 70 similar, 50 somewhat similar, 30 different, and anything lower very different.

delta_e is CIE76: both colors are converted from sRGB to CIE-LAB under the D65 white point and the Euclidean distance is taken there, so it tracks perceived difference more closely than the RGB figures. All distances and percentages are rounded to two decimals. are_identical compares the normalised hex strings, so #ff0000 and FF0000 match, but a shorthand value and its six-digit form do not. On the Free plan the distance, Delta E, HSL similarity and per-channel difference fields come back null.

What people use it for

Color Matching

Find and compare similar colors for design consistency and brand compliance

Image Processing

Compare colors in images for color correction and matching operations

Design Systems

Validate color palette consistency and identify similar colors in design systems

Quality Control

Compare product colors against standards for quality assurance and brand consistency

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON

Default REST response

XML

Markup format

YAML

Human-readable

CSV

Tabular export

Beta

GraphQL

Query language

New

MCP

For AI agents

Request parameters — GET /v1/colorsimilarity

Sent in the query string. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

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curl "https://api.apiverve.com/v1/colorsimilarity?color1=FF5733&color2=FF6B47" \
  -H "x-api-key: YOUR_API_KEY"

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Response — GET /v1/colorsimilarity

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

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{
  "status": "ok",
  "error": null,
  "data": {
    "color1": {
      "hex": "#FF5733",
      "rgb": {
        "r": 255,
        "g": 87,
        "b": 51
      },
      "hsl": {
        "h": 10.6,
        "s": 100,
        "l": 60
      }
    },
    "color2": {
      "hex": "#FF6B47",
      "rgb": {
        "r": 255,
        "g": 107,
        "b": 71
      },
      "hsl": {
        "h": 11.7,
        "s": 100,
        "l": 63.9
      }
    },
    "rgb_distance": 28.28,
    "rgb_similarity": 93.6,
    "hsl_similarity": 97.71,
    "overall_similarity": 95.65,
    "delta_e": 28.28,
    "hue_difference": 1.15,
    "saturation_difference": 0,
    "lightness_difference": 3.92,
    "similarity_category": "nearly identical",
    "are_identical": false
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

What a call costs — 1 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Zero-code embed — one snippet, no backend

Drop an interactive Color Similarity Calculator form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.

Changelog — Color Similarity Calculator API

Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.

Currently v1