Colour Approval: Lab Dips, Strike-offs, and Tolerance
Approve production colour on a defensible basis: set a colour standard, assess lab dips both visually under controlled light and instrumentally by colour difference, agree a ΔE tolerance, and guard against metamerism.
Reviewed colour-assessment references for controlled visual evaluation, grey-scale rating (ISO 105-A02/A03, AATCC EP1/EP2), colour-difference formulae (CIE76, CMC, CIEDE2000), and metamerism; no universal ΔE tolerance, illuminant, or approval decision is prescribed, and the buyer-supplier standard and agreement govern.
Colour approval decides whether a dyed or printed material matches an agreed standard closely enough for production. A lab dip is a small trial dyeing submitted against a colour standard; a strike-off is the print equivalent. Approve them on two legs, not one: a controlled visual assessment in a light box under an agreed primary illuminant (checked against a second light for metamerism), and an instrumental colour-difference reading against the standard. Agree the colour-difference formula and tolerance in advance, commonly a ΔE around 1.0 to 1.5 with CMC (2:1) or CIEDE2000, tightened for critical colours and loosened for hidden parts. Record the standard, illuminant, instrument, geometry, and result, because bulk production must then match the approved standard within an agreed shade band, not just match the lab dip once.
Colour is the most returned and most argued property in apparel, because "it looks right" depends on the light, the observer, and the substrate. A defensible colour approval replaces opinion with an agreed standard, an agreed light, and an agreed number.
Start from a defined standard
Approval is meaningless without a fixed reference. Agree, in writing, the colour standard (a physical swatch, a named colour system reference, or a measured digital standard), which face and area is measured, and the substrate, because the same dye reads differently on different cloth. A lab dip is judged against that standard, not against a previous lab dip or a screen.
Assess on two legs: visual and instrumental
| Controlled visual assessment | Evaluate in a light box under an agreed primary illuminant (for example D65 daylight, or a store light such as TL84), with a defined viewing geometry and a neutral surround, by an observer with normal colour vision. Rate the difference against the standard, often with a grey scale for colour change (ISO 105-A02, AATCC EP1) and for staining where relevant (ISO 105-A03, AATCC EP2). |
| Instrumental colour difference | Measure the sample and standard on a spectrophotometer and compute a colour difference, ΔE, against the standard. Record the instrument, aperture, geometry, illuminant, and observer so the reading is reproducible. |
| Both must agree | Instrument and eye can disagree, especially near tolerance. A number inside tolerance that the eye rejects, or vice versa, is a signal to investigate substrate, geometry, or metamerism, not to override one leg silently. |
Agree the formula and the tolerance first
| The formula matters | ΔE*ab (CIE76) is the simplest but agrees poorly with the eye. CMC (2:1) and CIEDE2000 (ΔE00) weight lightness, chroma, and hue to track perception far better, and are what most modern colour programmes specify. Name the exact formula; a ΔE is meaningless without it. |
| Tolerance is an agreement | A common commercial band is a ΔE around 1.0 to 1.5. Critical colours (brand reds, high-visibility, luxury) are often tightened toward 0.5 or less, while hidden linings and components may allow 2.5 or more. There is no universal number; it is set by risk and agreed by both sides. |
| Shade bands, not a single point | Bulk colour varies, so production is often controlled to a tolerance band (and sometimes physical corner or limit swatches) around the approved standard, rather than a single pass-fail point. |
| Component-consistent | Panels, trims, threads, and rib must read together on the finished garment; matching each to the standard separately is not enough if they clash side by side. |
Guard against metamerism
| Metamerism | Two samples can match under one illuminant and visibly differ under another, because their spectral curves differ even where the colours cross. This is why approval names a primary illuminant and checks under at least one secondary light. |
| Check multiple illuminants | Assess under the agreed primary light and at least one other (for example daylight plus a store or incandescent light). A pair that shifts between lights is a metameric match and is risky even if the primary-light ΔE passes. |
| Substrate and finish | The same recipe shifts on a different base cloth or after finishing, so approve on the production substrate and, where it matters, after the intended finish. |
This colour approval sits alongside colourfastness, which is a different question (whether the colour survives washing, light, and rubbing) with its own ISO 105 and AATCC methods; the cloth library entries note where those apply per material.
Colour-approval record
Lab dip / strike-off colour-approval record
Fix the standard, light, instrument, formula, and tolerance before submission, then record both the visual and instrumental result so the approval is reproducible.
Saved in this browser only, never sent to a server.
Standard and conditions (agreed before submission)
Submission result
Bulk control
Sources and decision boundaries
The visual-assessment, grey-scale, colour-difference, and metamerism practice here follows colour-measurement references including AATCC Evaluation Procedure 1, Gray Scale for Color Change, the Atlas guide to colour measurement (Technical Guide 103), and MFG Merch on mastering colour approval in apparel; the grey scales correspond to ISO 105-A02 and A03 and the difference formulae to CIE76, CMC, and CIEDE2000. The illuminant, formula, tolerance, and approval decision are a buyer-supplier agreement against a defined standard; this guide does not set a tolerance or approve a colour for any specific product.
Work with a technical designer.
When a colour "passes the number but looks wrong," suspect metamerism first: check the pair under a second light before touching the recipe. A metameric match that passes only under the light box will fail in the store and in returns.
FAQ
What is the difference between a lab dip and a strike-off?
A lab dip is a small trial dyeing of a fabric submitted to match an agreed colour standard before bulk dyeing. A strike-off is the print equivalent: a trial print of an artwork or pattern to approve colour, placement, and registration. Both are judged against a defined standard, not against a screen or a previous submission.
What ΔE tolerance should I use for colour approval?
There is no universal value; it is agreed between buyer and supplier by risk. A common commercial band is a ΔE around 1.0 to 1.5, tightened toward 0.5 or less for critical colours such as brand reds or high-visibility, and loosened to 2.5 or more for hidden components. State the formula too, since a ΔE without its formula (CMC, CIEDE2000, CIE76) is ambiguous.
Why does my colour match under one light but not another?
That is metamerism: two samples with different spectral curves can match under one illuminant and differ under another. It is why approval names a primary illuminant and checks under at least one secondary light. A metameric match that passes only in the light box is risky, so investigate the recipe rather than approving on the primary light alone.
Is instrumental ΔE enough on its own?
No. Approve on two legs: a controlled visual assessment under agreed lighting and an instrumental ΔE against the standard. Instrument and eye can disagree near tolerance, and a number that passes while the eye rejects the colour is a signal to investigate substrate, geometry, or metamerism, not to rely on the number alone.