Why do houses in Bermuda have white roofs?

All the houses and buildings and even the bus shelters in Bermuda have white roofs. This was one of the first things I noticed when arriving on the island, and I wounded why.

I have found out that they are all painted with a limestone powder mixture, so when rain water runs of the roof it gets sanitised on the way down and collected in a tank under the house. The water is then pumped out and used for everything you need water for in your home, you can even drink it, although I must admit I haven't as yet tried it.

Its a great idea as there is no other natural water souse on the island.