Daylight color demo

Why paint changes color through the day

Paint doesn't have one fixed color; it reflects whatever light hits it. Light has its own color, described as a color temperature in kelvins (K). Low numbers are warm and orange, like candlelight or a 2700K bulb; high numbers are cool and blue, like open north sky. Midday sun is in between.

• North-facing rooms in the northern hemisphere get mostly indirect skylight, which is cool and even. Colors look cooler and grayer.
• South-facing rooms get the most direct sun, especially in winter when the sun stays low; colors look warmer and brighter.
• East rooms are warm and bright in the morning and cooler later; west rooms are the reverse, with strong golden light in late afternoon.
• At night, your bulbs take over. 2700K–3000K bulbs warm everything up; 4000K–5000K bulbs look crisper and bluer.

Our eyes adjust to much of this, which is why the demo keeps the shifts realistic rather than dramatic. The practical lesson: test real samples on two walls and look at them in the morning, afternoon and at night before you decide. The full story is in our guide How light changes paint color.

This demo uses a simplified model of sunlight and skylight for about 45°N latitude (the St. Croix Valley) and typical sunrise and sunset times. It's for learning, not color matching.