Parts of rural northern  India  are currently exploding in color. Not just from the coming of spring, but seasonal festivals characterized by folk music, dancing, farmers in traditional dress, and dishes like sweet saffron rice.   Among them is Vaisakhi, which is an important festival date on the Sikh  calendar. Held in the northern province of Punjab, it marks the successful growth of winter wheat, and crops like mustard, chickpeas, lentils, barley and sunflower seeds.  "When the crop is fully