Mathura is the birth-place of Lord Krishna.When Krishna was young, he cribbed to his mother about Radha being fair while Krishna himself was dark complexioned. His mother suggested him to color Radha with colors in a playful manner. Over the years, Krishna from his village Nandgaon used to go to Barsana to color Radha and other Gopis. They also used to playfully beat him with sticks. And this gave rise to the tradition which is now famous all over the world.
Nikhil Jyani, Rahul Soni