It was a perception before, and the society is changing now and tilting towards earthy complexion. Dusky is definitely sexy now. Bipasha Basu, Kajol, Priyanka Chopra, Sameera Reddy, Lara Dutta, Mallaika Arora, Sonali Kulkarni, Raima Sen, Konkona Sen, Tanushree Dutta, Koena Mitra, Nandita Das, Jiah Khan and Geeta Basra are examples of earthy complexioned actresses who are very popular and extremely admired for their beauty and grace.
Check out the article http://bollywoodtrends.blogspot.com/2008/01/dusky-is-sexy-dusky-b ollywood-actresses.html for more information
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just as the people of countries which have majority people with fair skin have a liking for brown skin. whenever we go to tourist spots like goa, kovalam, or any sea resorts we see white skinned people (both men & women) taking sun bath just to become brown skinned