In various parts of the Mediterranean, such as in eastern and southern Spain, all of the houses in entire towns are painted white, in such a way that the sun is reflected off the walls of the houses, keeping them cool during the summer.
In Chefchaouen, a city in the north of Morocco, the color white is mixed with a large number of blues. With the arrival of the Jewish population in the 1930's, the color of the houses - traditionally the green of Islam - was changed to blue to scare off mosquitoes. This color creates a cold sensation, and they try to escape from it.
The same technique of using white to keep houses cool is used throughout the Mediterranean in Alberobello (Italy) or Grândola (Portugal); in other places such as Sidi Bou Said (Tunisia) or Mykonos or Santorini (Greece) white is also mixed with blue.
All of these are examples of how Mediterranean architecture has traditionally made use of these colors - blue and white - to provide both a cool environment, and an important public health service by keeping mosquitoes away during the summer.
This ancestral technique so common in the Mediterranean has served as inspiration for a Hundred White Cities initiative. Steven Chu, Minister of Energy of the USA and nobel laureate in physics, has argued for painting buildings' roofs white or light colors in order to fight climate change. Chu's proposal was inspired by a physics study done by Art Rosenfeld (member of the Energy Commission of California and expert engineer in energy efficiency). He and two other colleagues calculated that changing the colors of the surfaces in one hundred of the largest cities in tropical and temperate regions would save the equivalent of 24 billion tons of carbon dioxide a year.