How to choose a paint color?
Work from two numbers rather than a mood board: LRV, which tells you how much light the colour returns, and undertone, which tells you which way it shifts next to other colours. Then test a large physical sample in the actual room before you buy.
The two numbers that decide it
LRV runs 0 to 100. A north-facing room gets cool indirect light all day and pushes colours darker and cooler, so it usually wants a higher LRV than you first think. A south-facing room floods with warm light and can carry a much lower LRV without closing in.
Undertone is why two greys of identical lightness look nothing alike on the wall. A grey with a blue undertone reads cold and slightly purple in low light; the same LRV with a yellow undertone reads as greige. Our colour pages publish the measured undertone rather than describing it.
Paint a sample at least two feet square, or use a large peel-and-stick sample, and look at it at three different times of day. A chip held against a wall is judged against whatever is next to it, which is exactly the effect that makes people pick the wrong colour.
How we sourced this
This answer is composed from our knowledge base, which holds only what a regulator, a standards body or a manufacturer supports. The sources behind it are listed below with the date we accessed each one. If a claim on this page has no source under it, that is a bug — tell us and we will fix it.
Where a figure is product-specific — coverage, dry time, recoat time, temperature limits — we point you at the manufacturer's technical data sheet rather than printing a general number as though it were a specification. That distinction is the most common error in this trade, and it is the one that costs people a repaint.
Common mistakes
- Choosing from a chip held against the wall. The existing colour beside it shifts what you see.
- Testing a sample smaller than about two feet square. Small patches read lighter than the finished wall.
- Looking only in daylight, then living with the room at night under warm bulbs.
- Picking by name or by a photograph online. Names are marketing and photographs are colour-shifted by compression.
Related questions
Sources
- W3C. WCAG 2.2 — relative luminance (accessed 2026-08-17).
- Sherwin-Williams. Product technical data sheets (accessed 2026-08-17).
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- How to choose paint color?