The other story belongs to Krishna and Radha. It has been said that once when Radha came to meet Krishna, Chandrasena (I am not sure if I named him properly) husband of Radha came to know about it. So, when he came to fetch Krishna, to hide away from him, Radha colored Krishna with colors and that day we are celebrating as Holi festival.
He asked his sister, Holika to enter the fire with Prahlad so that he would be burnt as Holika was blessed with a boon by which she could not be hurt by fire. However, she was burnt when she entered the fire with Prahlad and Prahlad was safe since he continued praying his Lord and Lord was impressed with his devotion. Later Lord Vishnu in he form of Narashima killed the king, Hiranyakashyap.
On the day before the Holi, bonfire is there to celebrate the burning of Holika and on the day of Holi, people play with colours depicting the playing of pranks by Lord Krishna along with his gopis.