In the South Carolina Lowcountry, people have been painting the ceilings of their porches blue for generations. There’s even a name for the color: haint blue. According to Gullah legend, a haint is a spirit or a ghost. It’s said that if you paint your porch ceiling blue, it will welcome the good spirts and ward off the bad ones.
Some say the blue helps extend daylight as dusk begins to fall, and many believe that it helps keep bugs away. There’s no scientific research to back that theory up, but it makes sense to me. They say that insects prefer not to nest on blue ceilings because they are “fooled” into thinking the blue paint is actually the sky.
When blue paints were first used on ceilings, they were usually milk paints, and those paints often had lye mixed into the composition. Lye is a known insect repellent, which would explain why insects would avoid nesting on a painted porch ceiling or ledge. As milk paint has a tendency to fade over time, giving it a rustic look, people would usually need to repaint their home every year or few years, covering the existing coat with a new coat of paint, and fresh lye.