How light affects colour, and tips for choosing paint

A couple of weeks ago a reader asked me a few questions about the relationship between colour and light:

How do you relate the colours in a room and its orientation to the North, East, West or South ?
Should you use cool colours in a room that is oriented to the South, or warm colours?
Generally speaking, do you try to “compensate” the lack of light and sun, or too much sun, by using colours in the opposite range, or the other way around?

To answer these questions, we need to talk about colour temperature, an important characteristic of visible light. Colour temperature is basically the “hue” of light, and is measured in Kelvin degrees.

Imagine a black  piece of metal (black-body radiator) that heats up until it glows; at first the black-body radiator emits a dull red light, but with the increase in heat this light gradually turns yellow, then white, and finally blue. So the cooler the light, the higher its Kelvin value.

Candle light has a temperature  of about 1900 K and is quite orange; tungsten lamps have a yellow-white glow and a temperature of about 3,200 K. Fluorescent and energy-efficient bulbs tend to have a greenish tinge (45oo K), while the sun at midday has a white light (5500 K);  the darker  it gets, the cooler (i.e. blueish)  the light colour becomes.

Daylight varies dramatically depending on the weather, the season, the time of day, location and latitude. In general, though:

Rooms facing North receive a limited amount of cold, bluish light; this means that all shades of blue will be intensified.

If you want to maximize light, go for pale neutrals with a yellow or red undertone, and try to avoid colours with a grey base, as grey will make the room appear dull and gloomy. You can also go the opposite way  and decorate the room with deep colours like deep purples, reds or dark blues to create a dramatic, intimate mood.

Northern light stays pretty constant during the day, so the colours you choose won’t change too much.

Rooms facing South receive large amounts of warm light. These rooms are the easiest to decorate because Southern light works well with both cool and warm colours, and doesn’t change much during the day – like Northern light.

Keep in mind that light coming from the South makes colours appear very bright, so you can achieve an energetic mood even with muted colours.

Rooms facing East receive plenty of light in the morning, however the amount of light decreases as the day proceeds. Eastern light appears bluish and as the day progresses it appears even cooler, so it’s best to use cool colours like greens and blues, and off-whites with a blue or green undertone.

If your bedroom faces East, keep in mind that the colour you choose will appear very bright in the morning and duller in the evening; unless you have black-out blinds or shutters, sunrise might make the room too bright, especially in Summer. The opposite applies for kitchen and dining areas facing East, where a bright colour can create a vibrant, energizing mood for the start of the day.

Rooms facing West receive sunlight in the afternoon, so here the light will change from cooler in the morning to warmer in the afternoon. You can maximize light using neutrals with either cool or warm undertones. Grey undertones will work well too, although they will look cooler in the morning and warmer in the afternoon.

Remember that light also changes with the seasons, not just because there’s less available light in Winter, but also because the quality of the light  changes and becomes cooler, so the look of some interiors may alter dramatically.

In particular, West-facing rooms will be very bright and filled with light during the Summer, but during the Winter they’ll receive very little light since the sun sets so early.

The same is true for East-facing rooms, which will receive more light during Summer mornings than during Winter .

Another important point to remember is the quality of artificial light in the room; in general, fluorescent bulbs and energy efficient bulbs tend to give off a greenish tint, although some types of fluorescent lights have been improved and  are  now warmer. Halogen and L.E.D. lights generally emit the brightest and whitest light.

So how do you choose a paint colour for your room?

First of all, never choose a colour based on its name or on the colour you see on the tin! Get a  few paint cards from various suppliers, and look at them in the room you’re going to paint, both in natural and artificial light.

Once you’ve picked your favourite colours, buy small sample pots of paints and paint them on a board (at least 20 x 30 cm, or 8 x 12 in). Some suppliers even sell A4 cards already painted in their colour range.

Move the boards around the room, and see how the colours look during the day, both in daylight and artificial lighting. Check also how the colours look with the floor and furniture present in the room.

Before you decide, consider that if you paint all walls in a room in the same colour, the colour will be intensified – so a blue colour will look bluer, a red redder, and so on.

If you decide to paint a room in different colours (for example,  painting a feature wall in a different hue) check carefully how the two colours work together.

Finally, decide what finish you prefer, keeping in mind that gloss finishes reflect the light and make colours look brighter, while matt finishes reflect less light and make the colours appear more muted.

Last but not least: your existing paint colour will affect the appearance of the colour you choose, so unless your walls are already white, it’s best to first paint them with a white primer.

Here you can see a few examples of how light affects colour; I took shots of the same painted boards in East-facing and West-facing rooms in my house, for cold colours and neutrals. Colours are different in photos and in real life, but you can still see how paint changes in different lighting conditions.

East-facing room, mid- afternoon full light & shade

West-facing room, mid-afternoon full light & shade

East-facing room, mid-afternoon, full light & shade

West-facing room, mid-afternoon, full light & shade

If you want to know more about colour and light, check my other posts:

Design Basics Series: Understanding Colour

Design Basics Series: Understanding Light

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Tagged as: colour, interior design, tips