Why Jaipur called Pink City?

Jaipur is called the Pink City because at the time,In 1853, when the Prince of Wales visited Jaipur, the whole city was painted pink to welcome him during the regime of Sawai Ram Singh. Today, the houses remain painted in pink, provide a distinctive appearance to the city. 
Jaipur is called the pink city because most of the old buildings are painted in pink. 

old city of jaipur

http://travel.paintedstork.com/blog/2008/05/jaipur-old-city-may-their-souls-rest-in.html