re: Outdoor blue ceiling paint, fact or fiction?

Haint blue was a colour painted on doors and ceilings. The ghosts would confuse the colour believing that the ceiling was a part of the sky or the door a part of the water. The ghosts would think that the house is somehow protected with something sublime and powerful. This would confuse the ghosts unable to decipher how to enter the home. It was used as a protection colour from ghosts and spirits.

The blue came from the cultivation of indigo dye. It also kept bugs out because of the lye added into the paint that acted as a wood varnish and bug repellent. The lye paint mixture was particularly effective against wasps, spiders and infestations from building their nests or webs between the wood. Furthermore, if the bugs associated the colour with the sky, they would not make nests in the ceiling.