Color difference is quantified with the CIEDE2000 formula, a perceptually uniform metric that returns a single Delta E 00 value representing how far apart two colors appear to a human observer under a D50 reference illuminant. The formula, published by the CIE in 2001 and described in the ISO 13655 standard family, corrects known weaknesses of earlier Delta E calculations by weighting lightness, chroma, and hue separately and by rotating the hue difference term to match visual data. Because CIEDE2000 works in CIELAB space rather than RGB or HEX, every measurement begins with a conversion from the sRGB-encoded HEX input to D50-adapted CIELAB coordinates (L*, a*, b*). Once both colors live in that space, the formula combines the three coordinate differences through weighted root-sum-of-squares math, and the resulting Delta E 00 tells you whether two swatches are visually identical, subtly different, or clearly distinct.
Designers, developers, print technicians, and brand managers run into this calculation whenever a reference color needs to be checked against a produced color. A screenshot mockup must match a brand style guide. A printed proof needs to be compared to the original press sample. A logo imported into a new theme needs to feel the same as the old one. HEX values are easy to read and copy, but they are device-dependent rectangles in an RGB cube, not in the perceptual space the human eye uses. That is why a tool that converts HEX to D50 CIELAB and then applies the CIEDE2000 formula gives a far more meaningful answer than subtracting channel values.
What "Color Difference" Actually Means
The word "difference" is overloaded in casual color work. Subtracting the red, green, or blue channels of two HEX values gives a number that is not perceptually meaningful: a change of 10 in a red channel reads very differently than a change of 10 in blue, and the same numeric change looks different depending on the starting lightness. CIEDE2000 resolves this by computing distance inside a roughly perceptually uniform space, then printing the result on a single scale where larger numbers mean larger perceived gaps.
Reading the scale is straightforward once you know the bands the industry uses. Values under about 1 Delta E 00 are generally invisible to most observers under normal viewing conditions. Values between roughly 1 and 2 become noticeable only on close inspection of a controlled border. Values between 2 and 5 are clearly different but still acceptable in many design workflows. Values above 5 signal a mismatch that most viewers will spot immediately, and anything above 10 represents colors that share little perceptual ground.
Why HEX Is Not Enough for the Math
HEX is a six-character shorthand for an sRGB triplet, useful for CSS and design files but blind to the perception question. Two HEX pairs can produce a tiny channel difference that the eye perceives as a large color jump, while two HEX pairs with a much larger numerical gap can look almost identical. CIELAB was designed to fix this by mapping sRGB through a D50-adapted transform so that equal numerical steps in any direction look like roughly equal visual steps.
The reference illuminant matters too. D50 corresponds to a 5000 K daylight temperature and is the standard for the graphic-arts industry, which is why color-management pipelines from the ICC specification onward target D50 white. Working in D50 keeps your color-difference numbers comparable to proofs, press samples, and brand-specification documents that were measured under the same illuminant.
Run the Calculation in the Color Difference Calculator
The fastest way to get a standards-based Delta E 2000 number from two HEX values is the Color Difference Calculator. It accepts opaque six-digit sRGB HEX strings, converts each to D50 CIELAB internally, runs the full CIEDE2000 math, and shows you both the L*, a*, b* coordinates and the final distance so you can audit the result.
- Type or paste the first color into the left field as a six-digit sRGB HEX value, including the leading hash. For example, #1E6FBA for a mid-blue.
- Enter the second color into the right field in the same format, such as #1F70BB for a near-match reference swatch.
- Select Compare colors to trigger the conversion to D50 CIELAB and the CIEDE2000 calculation.
- Read the Delta E 00 value that appears in the result panel, then record both HEX inputs, the L*/a*/b* pair for each swatch, and the Delta E number alongside the tolerance band and viewing context for your workflow (for example, "monitor preview at 6500 K, target Delta E under 2 for production match").
Because every step runs locally and the math is deterministic, you can paste the same HEX pair back in tomorrow and get an identical number, which makes the record auditable in QA reviews.
Reading the D50 CIELAB Coordinates
The L*, a*, and b* values shown next to each swatch are not just an intermediate step; they are the perceptually meaningful coordinate triplet used by the CIE standard. L* runs from 0 (black) to 100 (white) on a lightness axis, a* runs from negative (green) to positive (red), and b* runs from negative (blue) to positive (yellow). Two colors with very different HEX values can sit close together in this cube, and two colors with similar HEX values can sit far apart, depending on where the lightness and chroma actually land.
When you inspect the coordinates, the per-axis differences (delta L*, delta a*, delta b*) often explain why a Delta E 00 came out the way it did. A large delta L* with small delta a* and delta b* describes a near-identical hue with shifted lightness, which is usually easy to fix by tweaking gamma or black point. A balanced split across all three axes typically indicates a true hue shift that requires re-mixing or re-inking rather than a simple exposure adjustment.
Choosing a Tolerance for Your Workflow
Different industries treat the same Delta E number very differently. The table below maps common tolerance bands to typical use cases. The exact threshold you adopt should always be written down next to the Delta E reading so reviewers can judge whether the result passes for that specific context.
| Delta E 00 range | Typical meaning | Common use cases |
|---|---|---|
| 0 to 1 | Not perceptible to most observers | Hard proofing, master prints, calibrated displays |
| 1 to 2 | Noticeable only on close inspection | Brand-critical UI elements, logo reproduction |
| 2 to 5 | Clearly different but often acceptable | General web design, photography, packaging proofs |
| Above 5 | Perceived as a clear mismatch | Out-of-spec prints, gradient banding, defective samples |
The numbers above are interpretive bands based on industry conventions, not strict standards. Specific jobs often set tighter or looser limits, so always compare against the tolerance your client or production house has signed off on.
Where This Fits in a Larger Color Workflow
Color difference is one step in a broader color pipeline that includes picking swatches, converting between color spaces, and building palettes. After you confirm a reference pair with the Color Difference Calculator, you may want to derive a matching scheme with the Color Palette Generator, translate the result into print-ready values with the RGB to CMYK Converter, or sanity-check a text-and-background combination using the Color Contrast Checker. For brand-spec work, the inverse color often sits next to the reference, which the Complementary Color Finder exposes in a click. If you need to translate HEX into the channel values used by your CSS, the HEX to RGB Converter keeps the data flowing without retyping.
For background reading on the CIEDE2000 specification and the D50 illuminant assumption behind it, the International Color Consortium's overview of color management is a reliable starting point. The ISO 13655 family of standards, which formalizes the measurement geometry for graphic arts, also describes how Delta E results should be reported so that values stay comparable across instruments and laboratories.
Tips for Reliable Delta E 2000 Readings
Always work in the same color space upstream. Mixing an sRGB HEX with a HEX that was actually authored in Display P3 will skew the conversion and inflate the Delta E number in ways that have nothing to do with the perceptual gap. If a brand spec lists sRGB, convert every asset to sRGB before measuring.
Watch the alpha channel. CIEDE2000 is defined for opaque colors, so translucent or premultiplied swatches need to be flattened to a known background before the formula is meaningful. The Color Difference Calculator requires opaque six-digit HEX inputs for this reason.
Record the viewing context next to the number. "Delta E 00 = 1.4" is incomplete; "Delta E 00 = 1.4, D50 illuminant, 2-degree observer, sRGB source, monitor preview" is a useful audit trail. That sentence is what lets a teammate a year later reproduce or challenge your measurement.
More on this topic: Create Perfect Color Gradients in Canva with One Tool.
For a deeper look, see Convert Hex Code to RGB in Illustrator in One Click.
For a deeper look, see Find Exact CMYK Matches Using HTML Color Names for DTF Printing.