# Choosing paint colour: light reflectance (LRV), room orientation and testing on the wall > What LRV is, what Portuguese manufacturers publish about colour and light, why you should test on the wall, and what dark colours change for coverage. - Page: https://paredecerta.pt/en/guides/colour-light-reflectance-choosing-paint - Language: English - Updated: 2026-11-04 ## Summary - LRV measures how much visible light a colour reflects, from 0 to 100. In the Portuguese catalogues we read (CIN, Robbialac, Barbot) we found no LRV values. - Daylight changes through the day and artificial light distorts colour. Robbialac advises choosing the colour in full daylight. - CIN and Robbialac ask for a colour test on the wall, because a printed card and a screen do not show the exact colour. - Dark or strong colours may need extra coats or a dedicated base, according to the CIN, Barbot and Robbialac data sheets. The same colour can look pale on one wall and dark on another. What decides it is the light entering the room, the paint finish and the colour already underneath. This guide explains light reflectance value (LRV), what Portuguese manufacturers say about colour and light, why you should test on the wall, and what changes with dark colours. *Updated on 4 November 2026. General information, not a substitute for an assessment by a professional.* ## The essentials - **LRV** says how much visible light a surface reflects. It runs from 0 (absorbs everything) to 100 (reflects everything). Paler colours have a higher LRV. - In the Portuguese catalogues we read (CIN, Robbialac, Barbot) we **found no LRV values**. Foreign manufacturers that publish them are a different matter. - Manufacturers warn that a printed card or a screen does not show the exact colour, and ask for a **test on the wall** before painting. - Daylight changes through the day. Artificial light also distorts colour. - Dark and strong colours may need **more coats** or a dedicated base, according to the data sheets. ## What LRV is The British standard BS 8493 defines LRV as the proportion of visible light a surface reflects, compared with the sensitivity of the human eye. It covers paint coatings and excludes, for example, fluorescent surfaces. Sherwin-Williams and Dulux Trade use the same 0 to 100 scale (Dulux calls it a 99-point index). Sherwin-Williams adds that paler tints have a higher LRV and that the glossier the finish, the more light it reflects. Robbialac says a matt finish absorbs more light and feels calmer and deeper. LRV measures **visible light**. It does not measure the heat of the sun. For facades, see [exterior facade paint](https://paredecerta.pt/en/guides/exterior-facade-paint-choice). ## What Portuguese manufacturers publish We read Robbialac's interior colour catalogue (2022 edition), CIN's Interior Colour Collection and Barbot's facade catalogue (2024). None gives an LRV. That does not prove the figure exists nowhere else in a manufacturer's documents. It means that, from what we read, you **cannot compare** it across brands or across Portuguese colour cards. If a foreign manufacturer gives you an LRV, treat it as an order of magnitude. It does not replace a test on your own wall. ## Light and room orientation Robbialac writes that the same colour can look different in sun and in artificial light: the cold white light of morning reveals the colour, afternoon light warms cool tones, and end-of-day light darkens colours. At night it depends on the bulb. It therefore advises choosing the colour **in full daylight**. On orientation, the sources we read do not say the same thing: | Room orientation | Robbialac (2022 catalogue) | Sherwin-Williams (room-direction page) | |---|---|---| | North | Preferably intense colours, to make up for the lack of sun | Least light all day. Avoid cool undertones, prefer warm ones and look at a higher LRV | | East | Cooler light, soft colours | Warm in the morning, cool in the afternoon | | South and west | Stronger light, refreshing tones such as blue or green | South: steady warm light. West: the reverse of east | Both say orientation matters, but they disagree on what to do: intense colour in a north room, or a higher LRV and warm tones. Treat them as style suggestions, not a rule. The Sherwin-Williams page is American, but Portugal is in the same hemisphere. Robbialac also mentions **back-lit** walls, which get less light: a pale colour gives continuity with the outside, a deep colour makes the room feel more intimate. ## Why a patch on the wall beats a card - In its interior catalogue, CIN warns that printing can cause slight differences from the original colour and always recommends a **colour test** before the final application. - Robbialac sells a 0.5 L Color Tester so you can apply a little paint and see how the colour reacts to the natural and artificial light of your home. It says perception varies with the light in the picture and the calibration of your screen. - In its catalogue, Robbialac says some colours are **metameric**: they change with the light source. If the same colour is tinted into products with different gloss, a visible difference may result. - Barbot offers a sample (Barbotester) to test at home. For facades it says colours vary with light and shade. How to test (common practice, not in the data sheets): paint a large square on two walls, let it dry, and look at it in the morning, in the afternoon and at night under the light you will actually use. ## Dark and strong colours: coats and coverage What the sheets say: - **CIN Vinylmatt** (revision July 2026): depending on the hiding power of the colour, the substrate and the contrast with the previous colour, **extra coats** may be needed. For some strongly contrasting colours CIN asks for a dedicated base (for example M787 for reds, F203 for blues, M788 for greens, P905 for yellows). The sheet warns that matt paint in dark colours can show whitish marks when rubbed and suggests VinylClean. Wait 28 days after painting before washing. - **Barbot 1943 Interior Matt Emulsion** (18/11/2024): over a dark colour, first apply 1258 Barboplac to hide the colour differences. - **Robbialac Robbiduro Acqua** (30/09/2022): for repainting medium or strong colours it advises the OpacPlus primer. In the darkest colours, drying can be slower because of the amount of colourant. We found no number of coats per colour. For litres, see [how much paint do I need](https://paredecerta.pt/en/guides/how-much-paint-do-i-need) and the [calculator](https://paredecerta.pt/en#calc). For finish by room, [which paint for each room](https://paredecerta.pt/en/guides/which-paint-for-each-room). ## Heat on a facade Barbot says in its facade catalogue that pale colours reflect more sunlight and dark ones absorb more, so a paint with good UV resistance is advisable. CIN has a thermo-reflective collection with solar reflectance proven in a study with the University of Porto's Faculty of Engineering, with no figures on the page. Council rules on colour: [painting the facade](https://paredecerta.pt/en/guides/painting-the-facade-licence-condominium). ## What we could not confirm - **LRV values** for CIN, Robbialac, Barbot or Dyrup colours: not found. - **The NCS system**: we did not read official documentation, so we do not explain it here. - **Number of coats for dark colours**: the sheets do not give one. - **Psychological effects of colour**: not used, for lack of a source. ## Sources (read on 4 November 2026) - BSI, [BS 8493:2008+A1:2010, Light reflectance value (LRV) of a surface: method of test](https://knowledge.bsigroup.com/products/light-reflectance-value-lrv-of-a-surface-method-of-test): summary and scope. Standard not read in full. - Sherwin-Williams, [How to Choose Paint Colors Based on Room Direction](https://www.sherwin-williams.com/en-us/project-center/paint/color-by-room-orientation) and [The Play of Light and Color](https://www.sherwin-williams.com/architects-specifiers-designers/education/paint-and-color-technology/sw-article-pro-theplayoflight): full text. - Dulux Trade, [Colour in construction](https://www.duluxtradepaintexpert.co.uk/colour-in-construction): definition of LRV. - Robbialac, [interior colour catalogue 2022](https://tintasrobbialac.pt/media/files/catalogo-cores-interior-2022): tips and notes sections; [Color Tester](https://loja.tintasrobbialac.pt/pt/robbialac/color-tester_p12010.html); [Robbiduro Acqua data sheet](https://tintasrobbialac.pt/download/ficha_tecnica/ROB_176/1/Robbiduro+Acqua-ficha_tecnica.pdf), 30/09/2022. - CIN, [Interior Colour Collection](https://cin.com/deco/ao/resources/documentos/InteriorColourCollection.pdf) (closing note); [thermo-reflective collection](https://cin.com/deco/pt/en/catalog-thermo-reflective-colours); [Vinylmatt 10-250](https://idoctec.cin.com/Home/Document/10250-DEC-CIN-BT-PT), July 2026. - Barbot, [facade catalogue 2024](https://barbot.pt/wp-content/uploads/2024/01/catalogo_fachadas_2024_web-barbot.pdf); [1943 Interior Matt Emulsion](https://barbot.pt/wp-content/uploads/2024/01/1943-FT-T.-Plastica-Mate-Interior-Branca.pdf), 18/11/2024. ## FAQ ### What is the LRV of a paint? The proportion of visible light the surface reflects, from 0 (black) to 100 (white). The standard BS 8493 defines the test method. ### Do Portuguese paints state the LRV? Not in the CIN, Robbialac and Barbot catalogues we read on 4 November 2026. We cannot confirm it does not exist in another document. ### Why test the colour on the wall? CIN warns that printing can slightly alter the colour and always recommends a test before final application. Robbialac says the same about screens. ### Does a dark colour need more coats? It can. The CIN Vinylmatt sheet (July 2026) says that, depending on the hiding power of the colour and the contrast with the substrate, extra coats may be needed. --- Source: https://paredecerta.pt/en/guides/colour-light-reflectance-choosing-paint. Independent information, not legal or tax advice.