New fabric stays cooler than white cotton—and it’s purple

With the dog days of summer nearing an end, many are counting down the days until they can give the darker clothes in their wardrobe a bit more love. Though plenty of people flout seasonal rules and wear all-black year-round, light-colored fabrics are typically the better choice during  hotter months because they reflect sunlight and can help keep us cool. This heat-reflecting logic is also partly responsible for the old decree, “don’t wear white after Labor Day!” But what