Choosing exterior colours that survive Perth light
2 August 2026 · 4 min read
Why the grey you chose indoors reads blue on the west wall, how much heat a dark exterior really adds, and the sampling method that prevents expensive mistakes.
Perth light is harsh, warm and very bright. It does things to colour that catalogue photography and showroom lighting do not prepare you for.
Why your grey went blue
Most fashionable greys are not neutral. They carry an undertone — blue, green, violet or brown — that is invisible under the balanced light of a paint shop and obvious on a west-facing wall at four in the afternoon.
Perth's afternoon light is strongly warm. Warm light exaggerates cool undertones by contrast. A grey with a blue undertone that looked sophisticated on a card reads distinctly lilac or icy on a sunlit render wall.
The fix is not to avoid grey. It is to test the specific grey on the specific wall.
How to read an undertone before you commit
Put the sample card next to a piece of plain white printer paper. Against true white, the undertone becomes obvious — the card that looked neutral will read visibly blue, green or pink.
Then do it again outdoors, on the elevation you are painting, at the time of day you most often see the house.
Sampling properly
Almost everyone samples wrong. The two mistakes are painting too small a patch, and painting it in one place.
The sampling method that works
Paint a minimum of A3 size, in two coats, on at least three separate elevations — one that gets morning sun, one that gets afternoon sun, and one in shade. Look at all three at three different times of day. A colour that works in all nine conditions will work.
Better still, paint the sample on a piece of primed board rather than the wall, so you can move it around, hold it against the roof, and stand it next to the fence and the driveway.
