No offense, but why is racism against dark skin popular in Indian culture when...?

Some of them are just as dark or even darker than the people they hate lol. I mean I have met alot of racist Indians, and alot that were even darker than me... yet they still are going to make fun of me because of my skin color... doesn't make sense. I used to be enemies with this Indian girl back in like middle school and one time she called me a "black beezy" yet she was about 3 shades or more darker. Whats up with that?