Delta E is not one context-free scale. Keep the formula and the input colour conditions with any reported difference used in a packaging review.
Name the actual calculation
Colour-difference formulae include the CIE 1976 L*a*b* Euclidean difference and more elaborate models such as CIEDE2000. They do not make every numerical difference directly interchangeable. The formula name belongs with the reported value. Primary reference: CIE: colour-difference formula scope.
Retain the input colour coordinates and how they were established, including the applicable measurement and viewing basis. A report saying Delta E equals two leaves important interpretation unresolved if another report used a different formula or a different physical observation condition.
Calculate an illustrative Euclidean case
For an invented pair of CIELAB coordinates with differences ΔL* = 3, Δa* = 4 and Δb* = 0, the simple Euclidean calculation gives √(3² + 4² + 0²) = 5. This is the stated CIE 1976 difference model for that hypothetical coordinate pair.
Do not label five as a CIEDE2000 result or as an acceptable packaging tolerance. The example supplies no actual colour measurement and no perception or acceptance guarantee. A different formula must be calculated according to its own model rather than being renamed after the arithmetic.
Keep criteria and observations compatible
When comparing supplier evidence, ask for the formula, reference sample identity and input-condition record. Confirm that the agreed limit uses the same stated basis as the reported result. A precise-looking number cannot resolve a mismatch between those definitions.
Review the actual printed task under the agreed appearance or measurement method and preserve the evidence behind the coordinates. If the method changes, document the new comparison instead of interpreting the old number on a new scale. This guide cites public CIE descriptions and a research example for the principle; it does not reproduce or certify a complete standard procedure.
Customer Questions
Are all Delta E formulae numerically identical?
No. Keep the named formula with the value.
Is the fictional result of five an acceptance limit?
No. It is one illustrative Euclidean calculation.
Does this guide certify a colour-measurement procedure?
No. The actual method and criteria require their own documented review.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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