A colour code can name an intended family; it cannot preserve substrate, gloss, texture, process, lighting or the physical appearance that the project actually accepted.
A window quotation says RAL 7016, the architect approves a phone photograph, and the supplier later submits a powder-coated aluminium chip. The code is familiar, the image looks close and the chip carries the same number. Yet the installed frames appear different beside adjacent cladding because the screen altered colour, the chip used another gloss and texture, and nobody retained the approved physical reference. The dispute began when four different tools—code, official card, project sample and digital image—were treated as interchangeable. A controlled approval gives each one a bounded job and preserves the actual reference used for production and batch comparison.
1. Give the code, card, project sample and screen image different jobs
Treat a RAL designation as a controlled communication reference within the specified RAL product/system and edition, not as an RGB value or a promise that every material will look identical. Record the exact designation, source product, edition or issue where relevant and whether the project means a classic colour, effect/metallic route or another collection. Do not copy a web hex value and label it an official RAL match.
An official physical colour card can provide a traceable system reference, subject to its condition and issuer instructions. A project sample goes further: it records the actual substrate, preparation, coating technology, colour, gloss, texture, directionality and application route proposed for the work. A production control sample or retained batch panel then records what was made. These references form a hierarchy only when the contract identifies which controls acceptance.
A screen image, PDF rendering or photograph is a coordination aid. Capture device, display calibration, white balance, compression, ambient light and surrounding colours can shift appearance. Use digital images to identify sample location, mark a concern or coordinate choices—not to replace a retained physical standard unless a qualified project method explicitly permits it.
| Reference | Useful purpose | Control fields | Cannot prove |
|---|---|---|---|
| Colour designation | Name an intended colour in a named system | System/product, code, edition/source | Exact appearance on actual substrate |
| Official physical card | System-owner physical reference | Authenticity, condition, issue and handling | Production finish, gloss or texture |
| Project physical sample | Approve proposed finish build-up | Substrate, process, colour, gloss, texture, ID | All future batches without comparison |
| Retained production/batch panel | Preserve manufactured comparison state | Batch/line/date and project-sample link | Installed appearance in every light |
| Screen image/photo | Communication and location context | File/source/device limitations | Authoritative colour match |
2. Write a sample brief before asking whether the colour looks right
Tie the request to project, component and finish: profile or panel material, alloy or substrate route where applicable, preparation, coating/finish system, colour designation, gloss and texture, directional or metallic effects, extrusion/flat-panel geometry and adjacent materials. Define sample size and form only through the project/coating route; a flat chip may not represent edges, recesses, welds, corners or extrusion shadows.
Give every submitted object a unique ID and record manufacturer/applicator, product system, batch or trial reference, date, substrate and process. Mark front/back and orientation where appearance is directional. Do not write approval on the only sample and return it without retaining an identified project-controlled reference.
State the decision requested: colour-family selection, finish-system approval, appearance mock-up, production-range reference or batch disposition. A colour selection should not silently approve durability, coating quality, substrate preparation, compatibility, process capability or installed workmanship.
| Field | Controlled entry | Open risk if missing |
|---|---|---|
| Reference system | Exact code/product/edition | A familiar code points to unlike references |
| Substrate/profile | Material, shape and preparation route | Flat card masks actual geometry/substrate |
| Finish build-up | Named coating/process, gloss, texture/effect | Same colour name looks materially different |
| Sample identity | Unique ID, maker/applicator, batch/date | Object cannot be retrieved or repeated |
| Decision scope | Colour / finish / mock-up / batch purpose | Approval expands beyond observed scope |
| Retention | Owner, storage, validity and supersession | Production compares to memory/photo |
3. Control viewing conditions and record metamerism instead of arguing from memory
Define a visual-comparison method through the project specification and applicable standard: authorised observers, light sources or daylight conditions, surrounding/background, orientation, viewing geometry and sample conditioning/cleanliness. ISO 3668 addresses visual comparison of the colour of paints; ASTM D1729 covers visual appraisal of colours and colour differences. Citing them does not select project conditions or acceptance limits.
Compare the proposed sample with the retained reference and relevant adjacent materials under every agreed critical lighting condition. Materials can match under one light and separate under another; gloss, texture, curvature and metallic direction can change perceived lightness and colour. Record the condition and observation rather than declaring one sample universally identical.
Instrumental colour data can support production control only under a defined instrument, geometry, aperture, calibration, measurement locations, colour space/difference formula and surface restrictions. ISO/CIE 11664 addresses colorimetry fundamentals; it does not make one numerical tolerance suitable for textured, metallic, anodized, curved or mixed-material finishes. Keep visual and instrumental decisions distinct and authorised.
| Control | Defined condition | Actual record | Decision limit |
|---|---|---|---|
| Physical references | Retained IDs and condition | Compared objects | Only named objects |
| Illumination | Approved sources/time/weather where used | Observed condition | No cross-light extrapolation |
| Geometry/background | Orientation, angle, surround | Setup/photos | No uncontrolled photo decision |
| Visual observers | Authorised roles and method | Independent observations | No memory-only verdict |
| Instrumental route | Instrument/geometry/calibration/locations | Raw results and method | Project-defined formula/limit only |
| Metamerism/effect | Critical lights/directions | Observed change | Escalate, do not average away |
4. Issue a bounded disposition and retain the reference
Use defined states: approved for named finish and application; approved subject to a named correction and resubmission; rejected against a stated reference; or held pending adjacent-material/light review. Record approver authority, date, reference IDs, conditions, scope, exceptions and superseded samples. ‘Looks good’ in chat is not a production release.
Seal, label and store the retained reference as the finish manufacturer recommends, protecting it from light, abrasion, contamination, humidity or handling that could change appearance. Keep an issue log for any duplicate working samples and periodically verify condition. If the standard ages, becomes damaged or is lost, hold new comparisons until an authorised replacement/correlation is established.
Incorporate the disposition into finish schedule, drawings/BOM, purchase order and production release. One physical sample must not compete with an outdated code in the contract or a different gloss in the supplier order.
5. Compare production batches without turning one chip into a blanket guarantee
Define production lots or batches from the actual coating/applicator process and project traceability. Retain identified panels or representative profiles where the approved plan requires them and link batch, line/run, substrate, cure/process evidence and affected opening marks. Avoid mixing batches across one elevation without authorised appearance review.
Inspect production under the same controlled visual/instrumental route used for approval. Include representative extrusion faces, orientations, corners or assembled relationships where geometry affects appearance. Record variation within a part, between parts and against the retained standard separately.
At site, distinguish batch variation from lighting, orientation, protective film, contamination, wetness, adjacent colour and damage. Preserve evidence before cleaning or replacement. A factory batch pass does not promise that every installed view will appear identical under every condition.
| Batch control | Evidence | Affected scope | Disposition |
|---|---|---|---|
| Applicator/run | Supplier, line/run/date and process record | Profiles/components | Accepted/held |
| Retained batch reference | Unique panel/profile ID and storage | Named batch only | Comparison basis |
| Project-standard comparison | Controlled viewing/measurement record | Inspected sample scope | Pass/hold/NCR under approved rule |
| Opening allocation | Batch to component/opening marks | Elevation/zone | Mixing review |
| Site observation | Lighting/orientation/film/condition context | Observed openings | Investigate without causal shortcut |
FAQ
Is a RAL number enough to order window colour?
No. Record the exact RAL system/product and add the actual substrate, finish technology, gloss, texture, sample and approval route.
Can a phone photo be approved as the colour standard?
It is normally only communication evidence because capture and display conditions alter appearance. Retain the physical reference required by the project.
Does an official RAL card represent powder-coated aluminium exactly?
It represents its official system reference within its product scope; actual finish appearance also depends on substrate, gloss, texture, process and geometry.
Should colour be checked only in daylight?
Use every lighting condition defined by the authorised project method. One daylight view or booth setting may not reveal metamerism or effect differences.
What Delta E should be accepted?
This guide provides none. The finish type, instrument/method, formula and authorised project specification must define any numerical limit.
Can the approved project sample be returned to the supplier?
Keep a controlled retained reference, and issue identified working copies only through a correlated process. Do not leave approval dependent on one untracked object.
Does colour approval approve coating durability?
No. Appearance, finish-system specification, process quality and durability evidence are related but separate decisions.
Continue the project review
Connect this guide with the proposed window and door systems, then review how Cavorlen approaches manufacturing and quality control. When your schedule is ready, send it through the project review form.
Official sources used
RAL Colours — official colour communication and products ↗ISO — ISO 3668:2017 visual comparison of colour of paints ↗ASTM International — ASTM D1729 visual appraisal of colors ↗ISO/CIE — ISO/CIE 11664-1:2019 colorimetry, standard observers ↗ISO/CIE — ISO/CIE 11664-4:2019 CIE colour space ↗Related buyer guides
This article is general colour-communication, sampling and evidence-control education. It is not a colour specification, coating selection, colourimetry method, visual-acceptance standard, tolerance, warranty determination or defect decision. It supplies no RAL colour, gloss, texture, substrate, coating thickness, instrument geometry, illuminant, observer, viewing angle, distance, colour-difference formula, Delta E value, batch limit, sample size or acceptance threshold and does not reproduce proprietary RAL colour values or state any Cavorlen finish, supplier, capability, sample, tolerance or policy. The official colour-system owner, exact coating/finish manufacturer, project specification, retained physical standards, agreed viewing and measurement method, and named design/technical authorities must define and approve the actual colour route.