The same applys to houses. The lighter/more reflective your roof, the cooler the rooms beneath it remain. It works in cooler regions too, using darker colours to increase temperature.
The difference colour can make is startling. On a 32.2 C clear sunny, day in Austin Texas, a white roof had a temperature of 43.3 C,
an aluminum coated roof was 60 C,
while a black, single ply roof, had a temperature of almost 87.8 C
A study in Florida revealed that by increasing heat reflectivity, homeowners saved an average of 23% if their cooling costs. That could make a big difference in the long run.
The lighter the color the higher the reflectivity. Dark walls absorb more light and reflect less. Consequently, far more lighting is required for rooms with dark walls than those with light walls. In addition to the walls, it is a good idea to keep the ceiling light and bright for good reflectance.
Most major paint manufacturers can tell you the Light Reflectance Value (LRV) of any color paint chip. White reflects 80% of the light, black 5%. Therefore, the higher the LRV number of the paint color, the less artificial light you will need.
Caution: Don't go overboard. An extremely high lighting level combined with very light walls is bad if it creates glare and / or too much brightness on the wall. This causes excessive stimulation and irritation of the eyes. Eye fatigue will follow.
I thought this was particularly interesting considering I am cold all the time (my living room is green, blue and white): The color of a room will affect your perception of temperature. Tests document that people estimate the temperature of a room with cool colors, such as blues and greens, to be 6-10 degrees Fahrenheit cooler than the actual temperature. Warm colors, such as reds and oranges, will result in a 6-10 degrees Fahrenheit warmer estimate.
In these ways colour can play an important role in energy conservation.