Frequently asked questions

SNKI is the Netherlands Colour Institute: an independent non-profit foundation that collects, develops and applies knowledge about colour for companies, designers and public authorities. The institute advises on colour in production and design, measures and assesses colour, trains and tests colour assessors, acts as an independent expert in colour disputes and develops colour standards. SNKI also supplies the RAL and NCS colour systems for the Benelux, publishes a knowledge base on colour science and provides education through the Dutch Colour School (Nederlandse Kleurenschool). The organisation dates back to 1976, when Maas Kotterink founded the consultancy Total Color Technics. The Dutch Colour School followed in 2008 and the current foundation in 2018.

SNKI is based in Krommenie and receives visitors by appointment in Amersfoort. The registered address is Van Allenstraat 110, 1562 TN Krommenie, the Netherlands. Appointments take place at Disketteweg in Amersfoort (Celciushuis), within walking distance of the railway station and with ample parking. Call +31 (0)75 616 99 77 or e-mail info@snki.nl to make an appointment. Visits without an appointment are not possible.

SNKI helps companies achieve, control and prove the right colour: with advice, measurements, training, independent assessment and the associated products. The institute offers eight services:

• Colour recipe formulation: system optimisation and recipe formulation.
• Product Color Management: colour consistency in production, from standard to process control.
• Color Standard Development: physical and digital colour standards for your own colours.
• Colour Dispute & Arbitration: independent measurement and reporting in disputes.
• Brand Visual Identity: brand colour consistent across all materials.
• Training & Testing: training colour assessment and testing colour discrimination.
• Project support: guidance in setting up or improving your colour quality system.
• Instrumentation & Advice: independent advice on instrument selection and validation.

SNKI also supplies light booths, colour measuring instruments, ceramic colour standards for validating spectrophotometers, the RAL and NCS colour systems and custom colour products. The knowledge base contains more than eighty articles on colour measurement, colour assessment and colour application. Courses and training programmes are offered by the Dutch Colour School.

SNKI works for every sector in which colour is a quality requirement, from paint and coatings to construction, healthcare and architecture. The institute assesses and measures colour on paint and coatings, plastics, textiles, metal and anodised aluminium, concrete, façade cladding and floors. Clients include manufacturers, contractors, architects and interior architects, municipalities and healthcare institutions. Examples from practice: colour standards for the anodising process for Qualanod, a tolerance framework for aesthetic concrete repair for a municipality and an independent judgement on façade panels for a manufacturer.

Yes. SNKI works worldwide. Measurements, assessments, training and independent reports are carried out on site, in the Netherlands and abroad. SNKI works with the international standards for colour measurement and colour assessment, so reports can be used anywhere. For RAL, SNKI is the distributor for the Benelux; for NCS, SNKI is an independent specialist and supplier of original NCS products. An example of international work is the masterclass on colour standards in the anodising process for Qualanod.

Yes. SNKI comes to your company or project for measurements, assessments, training and the testing of assessors. Colour measurements are taken on site with a spectrophotometer, on the reference samples and on the surfaces concerned, always combined with a visual assessment. This can be done in production, on a construction site or at a façade. Training in colour assessment is delivered in-company, tailored to your products and your working methods, and the testing of colour assessors takes place at your location. If it concerns individual samples or colour swatches, you can also send them in; SNKI measures them and reports the outcome.

Yes. SNKI supplies light booths, spectrophotometers and colour meters and gives independent advice on the choice that suits your material and your working methods. The range consists of light booths for visual colour assessment under standardised light, portable colour meters and spectrophotometers from Datacolor, DigiEye for non-contact colour measurement and image analysis, and ceramic colour standards for validating your spectrophotometer. SNKI is not tied to any manufacturer. The advice is about the right instrument, the right measuring geometry and the validation of your equipment, not about a brand.

Yes. SNKI develops colour standards for colours that do not exist in RAL, NCS or another reference system, and produces fan decks, colour cards and displays with your own colour collection. A custom colour standard starts with the colour choice and ends with a physical sample with spectral data and a defined tolerance, so that your manufacturer and your quality department work with the same reference. For your collection as a whole, SNKI produces custom colour products: fan decks, colour cards, colour labels, wood and plaster samples and displays, manufactured to your specifications. An example from practice is the adaptation of the colour standards for the anodising process for Qualanod.

A reliable colour assessment requires standardised light, a neutral surround, a trained assessor and a measurement that supports the visual assessment. In the Netherlands the international standards apply. SNKI works according to ISO 3668 and ASTM D1729 for visual colour assessment, ISO 3664 for viewing conditions and light booths, and CIE colorimetry (CIELAB, CIEDE2000) for colour measurement. Sectors also apply their own standards, such as AATCC EP9 in textiles. SNKI advises on setting up your colour assessment: the right light booth, the working method, the tolerances and the requirements for the assessor.

This happens more often than you might think and usually has an identifiable cause. A spectrophotometer measures one spot under one geometry; the eye sees a whole surface, under the light and the angle of that moment. Metamerism, gloss, texture, measuring geometry and the light on site can all produce a difference that the instrument does not show, or the other way round. SNKI investigates where the difference comes from, with measurements and a visual assessment under standardised conditions, and advises on how to prevent it in your process. An example from practice: two identical façade panels that differ visually but not when measured.

Which ΔE is acceptable depends on the product, the material, the colour itself, the measuring method and the agreement between client and supplier. A tolerance that works for a powder coating is useless for anodised aluminium or textiles. The colour difference formula used also matters; ΔE2000 gives a different figure from ΔE76 for the same difference. SNKI advises on a tolerance that suits your product and your process, and records it together with the measuring conditions, so that both parties measure the same thing.

With a standardised test of colour discrimination, followed by training in assessing under fixed conditions. SNKI tests employees with ColorAptitude, an assessment platform for colour discrimination. The result shows per colour region where someone is strong and weak and provides a demonstrable qualification of the assessor, as required by ASTM E1499. SNKI then trains assessors in assessing under standardised conditions, distinguishing relevant from irrelevant colour differences and using the instrument alongside the eye. This takes place at your location, tailored to your products.

Engage an independent expert who measures and assesses the colour difference under standardised conditions. SNKI measures the samples and surfaces concerned with a spectrophotometer, assesses them visually, tests the difference against the agreed tolerance and the applicable standards, and records the outcome in a report that both parties can use. Because SNKI is not tied to any manufacturer or supplier, the judgement is usable for both sides. SNKI also advises on recording colour agreements in advance, so that a next dispute does not arise.

Yes. SNKI acts as an independent colour expert in objection procedures, permit matters and court proceedings. The judgement rests on measurements according to international standards, a visual assessment by a qualified assessor and a report in which method, measuring conditions and conclusion are recorded. SNKI also advises municipalities and aesthetics committees themselves on colour in the built environment, for example on tolerances for concrete repair or façade colours. Two examples from practice: a house in Amstelveen that was allowed to stay blue, where the court ruled against the municipality, and a tolerance framework for aesthetic concrete repair commissioned by a municipality.

RAL is a colour system with three collections of numbered colours; NCS is a colour system that describes every colour as the eye perceives it. RAL Classic is the reference for coatings, window frames and building products, because manufacturers carry those colours as standard. RAL Design System plus is organised by hue, lightness and chroma and is intended for design and architecture. RAL Effect is the collection for industrial coatings, with solid and metallic colours. NCS describes a colour by blackness, chromaticness and hue and has 2,050 standardised colours; it is the system for colour design and colour advice, where the relationship between colours matters. Converting between the two is always an approximation. SNKI supplies both systems and advises which system suits your application.

RAL and NCS are independent colour systems; ACC and Voice of Colour are colour collections of paint manufacturers. A colour system is product-independent: the colour is defined separately from any brand or material, and every manufacturer can work to it. That makes it usable as a common language between client, designer and manufacturer, even when several suppliers or materials are involved. A manufacturer collection is tied to the products of that manufacturer. SNKI does know those collections: the Colour conversion tool converts a colour to Sikkens, Sigma and Flexa, among others.

Yes. With the Colour conversion tool on this site you convert a colour code to RAL, NCS, Munsell, Pantone and the collections of paint manufacturers. You enter a code or hex value and see the closest colours per system, with the colour difference in ΔE2000, so you know how far the colour found really is from the original. Every conversion is an approximation: a colour from one system rarely exists exactly in another. If you have a physical sample whose colour you want to know, you can send it in; SNKI measures it and determines the closest colour.

Yes. SNKI publishes professional books and a knowledge base with more than eighty articles on colour measurement, colour assessment and colour application. The three-part series Kleurbeoordelen in de Praktijk (Colour Assessment in Practice, SNKI Publishing, 2025) covers the theoretical foundations, colour measurement and assessment, and sector-specific applications; the series is written for professionals in production and quality control. Kleuren kiezen voor de gezondheidszorg (Choosing Colours for Healthcare, SNKI Publishing, 2026) is about colour in care environments. The knowledge base is freely accessible and organised by theme: colorimetry, colour measurement, visual colour assessment, colour quality, colour systems and colour psychology.

At the Dutch Colour School (Nederlandse Kleurenschool), the educational branch of SNKI. The Colour School offers five professional programmes in Amersfoort: Colour Science/Colour Advice, Colour Design, Colour Assessment, Colour Making and Pigments. There are also online courses, including on NCS, RAL, general colour theory and colour psychology, and one-day workshops, such as colour in healthcare and colour in interior architecture. The teaching is brand-independent and scientifically founded. The Colour Advice and Colour Design programmes conclude with an examination and give access to the register of colour experts. For companies, SNKI provides in-company training and the testing of assessors.

Anyone may call themselves a colour expert; the register of colour experts shows who holds a recognised diploma. Anyone who has obtained the Colour Advice or Colour Design diploma from the Dutch Colour School is listed in this register with their own registration code. On the verification page you enter that code and immediately see name, register title, year and status. The register has two titles: Kleurkundige (Colour Specialist), for the Colour Advice diploma (Dutch vocational level 3), and Register Kleurvormgever (Registered Colour Designer), for the Colour Design diploma (Dutch vocational level 4). Registrants can place a badge with their code on their own website; it links to the verification page. The full register list is public. SNKI has managed the register since 1 August 2025; before that it was the quality register of the BNK Foundation.