Light is one of your colour decisions

The materials you choose are only half of what you will see. The other half is the light on them, and part of that decision must be made before the plaster goes on, long before anyone thinks about colour.

Three decisions, at three different times

Lighting is usually treated as one decision. In a renovation it is three, and getting the timing right matters more than any particular product.

Before the walls closeColourwise guidance: Where light falls: task lights over worktops, a mirror light, wall lights and separate circuits. Moving these later means chasing walls or lifting tiles.
Before final paintColourwise guidance: The actual lamps. Fit them, or a sample of them, before settling the wall colour, because that colour will spend its evenings under them.
After you have lived with itColourwise guidance: Dimming and lamp changes. This is the cheapest correction in a finished room, and often the first thing to try if a colour looks wrong.

Daylight by orientation

The direction of a window shapes a room’s daylight. This shows the direction of the effect in the northern hemisphere. Reverse north and south in the southern hemisphere.

The ring is neutral. A bar outside it shifts colour warmer, and a bar inside it shifts it cooler. Lengths are an ordinal comparison, not a measurement.

North-facing: In the northern hemisphere a north-facing room never receives direct sun, so it is lit by sky rather than sunlight — steady, soft and distinctly blue. Cool colours go colder and greys can turn faintly violet; warm colours lose some of their warmth but gain a subtlety they do not have in direct sun.
East-facing: Bright warm light in the morning, then indirect and cooler for the rest of the day. Worth deciding which half of that day the room is actually used in, because the two halves are genuinely different lighting conditions.
South-facing: Direct sun for much of the day, warm and strong, and shifting markedly from morning to evening. Colours here are seen at their most saturated and their most variable — a south-facing room is the one place a colour genuinely does look different at different hours.
West-facing: Cool and indirect for most of the day, then strongly warm and low-angled in the late afternoon. Colours can look flat at midday and unexpectedly rich at five o'clock.

Choosing lamps with colour in mind

Two numbers on the box are worth understanding. Neither predicts exactly how your wall will look, and together they still leave plenty out.

Colour temperature (CCT)Physical mechanism: Describes whether a lamp looks warm or cool. Lower values look warmer. Two lamps with the same CCT can still make colours look different, because CCT says nothing about the spectrum behind it.
Colour rendering (CRI)Sourced research: An index of how closely a lamp renders a set of test colours compared with a reference light. It is a helpful filter, but it is one number standing in for a whole spectrum, and a high score is not a guarantee for any specific colour.
Spectral limitsPhysical mechanism: A surface can only reflect wavelengths the lamp provides. If a lamp is weak in part of the spectrum, the colours that depend on it look duller, and no paint can make up for that.
Mixed lightPhysical mechanism: Daylight and lamps often light a room together, so one wall can be cooler near the window and warmer near a lamp. Eyes adapt to one or other, so the mix can look wrong even if neither light would on its own.
Task and ambientColourwise guidance: A worktop needs direct light, and a room needs general light. Use the same colour temperature for both unless you have a reason not to, so that one surface is not lit in two colours.
GlossPhysical mechanism: A glossy surface shows the lamp as a highlight. A matt one shows only the colour. Lamp position therefore matters more in a room of glazed tile and polished stone.

Day and night are different rooms

This is the direction of the change only. A real lamp and a real surface will differ, so use it to understand what to look for, then test the actual pair.

Each row is one surface, and each column shows the direction it shifts under a condition.
Surface	Bright daylight	North sky	Cool LEDs	Warm evening lamps
Warm white
Blue-based grey
Oak
Navy

For material-by-material detail, see the light and finish matrix.

Going further

How to read the labels on this page

Physical mechanism:: How light, surfaces or colour vision behave. The direction is reliable; the size varies from room to room.
Sourced research:: Reported in a publication listed in the sources at the end of this page.
Design convention:: A widely held design habit. Worth knowing, and worth ignoring when you have a reason.
Colourwise guidance:: Our own working advice, reasoned from the mechanisms above. Not a measurement of your room.

Sources

CIE 013.3-1995 Method of Measuring and Specifying Colour Rendering Properties of Light Sources, CIE
ANSI/IES TM-30-24, IES Method for Evaluating Light Source Color Rendition, Illuminating Engineering Society (via ANSI Webstore)
LED Basics, U.S. Department of Energy, Solid-State Lighting Program
What is gloss and how is it measured?, Rhopoint Instruments