Every white has an undertone
Very few whites are pure white. Most carry a small amount of another colour, and that undertone decides how the white behaves. Whites with a yellow or red base read warm and soft. Whites with a blue, green or grey base read crisp and cool. On a chart, held next to other whites, the difference is easy to see. On its own on a wall, you mainly notice it as a feeling: cosy, clean, stark or flat.
The undertone is not a fault to avoid. It is the thing you are actually choosing. The useful question is which undertone suits the light in the rooms you are painting.
Which way the room faces
In Melbourne, a north-facing room gets the sun for most of the day, and that light is warm. It pushes a warm white further towards cream, and it can make a cool white look fresh and balanced. A south-facing room gets softer, indirect light that is cooler and greyer. In that light a cool white can look dull or slightly blue, while a warmer white holds onto its brightness.
East-facing rooms are bright and warm in the morning and flatter in the afternoon. West-facing rooms are the reverse, with strong warm light late in the day. This is why one white carried through a whole house can look like three different colours, and why some people deliberately use a slightly warmer white in the south rooms so that the house reads as one colour.
Globes, sheen and what is next to the wall
Artificial light changes a white as much as daylight. Warm-white globes pull a white towards yellow; cool-white or daylight globes pull it towards blue. If the room is mostly used at night, look at the samples under the globes you actually have, not only in daylight.
Sheen matters too. The same white in a flat finish on a ceiling and in a gloss on the skirting boards will look slightly different, because the glossier surface reflects more light. Colour also bounces: a green lawn outside the window, red brick across the yard, timber floors or a coloured feature wall will all tint the white on the walls next to them.
Why the chart is not enough
A colour card is small and is usually viewed against white paper under shop lighting. Spread across a whole wall, a colour tends to look lighter and its undertone more obvious. That is the main reason people are surprised once the first coat goes on.
The reliable way to choose is to see the white where it will live. Paint a sample patch, or a sample board, that is at least the size of a sheet of A3, on two different walls of the room, away from the old trim colour. Look at it in the morning, in the afternoon and at night with the lights on. Put the two or three whites you are deciding between side by side, and the undertones become obvious.
Walls, trim and ceilings
Many homes use one white everywhere, changing only the sheen between walls, trim and ceiling. That is simple and it works. Others use a slightly brighter white on the trim so that the doors and skirting stand out a little against the walls. Either is fine. What matters is that the decision is made deliberately and written into the quote, so the walls, trim and ceilings are each quoted in the white and sheen you have chosen.
If you are unsure, it is worth settling the white before booking the job. Changing it after the first room is painted costs time and an extra coat.
Frequently Asked Questions
Why does my white paint look yellow or grey on the wall?
Because of its undertone and the light in the room. A warm white in a sunny north-facing room can read creamy, and a cool white in a south-facing room can read grey. Warm or cool light globes and colour reflected from floors, gardens or brick change it as well.
Should I use the same white in every room?
You can, and many homes do. If the south-facing rooms make it look grey, a slightly warmer white in those rooms can make the house read as one colour. Test the samples in the rooms where they will go before deciding.
How should I test a white paint before committing?
Paint a sample patch or board at least the size of a sheet of A3 on two walls of the room, away from the old trim colour, and look at it in the morning, in the afternoon and at night under your own lights. Compare two or three whites side by side.
Does the sheen change how a white looks?
Yes. A glossier finish reflects more light, so the same white looks slightly brighter on gloss trim than on low sheen walls or a flat ceiling.