Indians - generally - are obsessed with anything foreign. The obsession with foreign products, westernised standards of living, foreign degrees and working in another country. You see a white-skinned foreigner in India, whether he/she's a gypsy, a software engineer or a tourist there's an enigma surrounding him/her and the crowd just stares.
What I'm getting at is, whether the white skin is a factor or not, Indians are just as racist to other Indians in the presence of white skinned foreigners.
I'll cite an incident that was told to me by my good friend and mentor, Prof. CV Ramakrishnan (father of the 2009 Nobel Prize winner, Venkatraman Ramakrishnan). He's been suffering from leukoderma from the past 30 years and today, more-or-less resembles a white-skinned foreigner.
He was the chief guest for the National Diabetes meet up at Hyderabad a couple of years ago. There were scientists from all over the world (all Indian origin though), some very successful ones with lots of international publications. After the inauguration, the press comes to Prof and tells him that they want to take a couple of photos of him and an interview. Prof says, "Haha, why me! I'm just an old man who has stopped his research in the past 20 years, it's better if you interview X, Y, Z... [Insert Indian names] who have done phenomenal research in the field of diabetes."
The fawning interviewers, "No Sir, we'd like to take your interview only. It will be published day-after tomorrow."
Prof naturally flattered by this point of time accepted.
[Interview starts]
Interviewer: Sir, could you spell out your name please?
Prof: It's Ramakrishnan. R a m a..
Interviewer: Come again, Sir.
Prof: Ramakrishnan. R a m a..
The interviewers looked baffled, looked at each other and asked the following question.
"Sir, are you Indian?"
Prof replies saying of course he is.
No interview was taken. The interviewers quickly said their thanks and left the building.
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This is a classic example of how white skin in India indicates something foreign, something different, something apparently "more attractive". Another aspect as to why Indians are more racist towards darker skinned people.