Holi is an ancient celebration, unheard of to anybody in the West, as basic as our Christmas or Easter to people in India.
It is a tribute to one devotee's faith in the Master, and how that faith was enough to transcend death itself:
In legendary times the child Prahlad was a great devotee of the Lord. His evil sister Holica was jealous of his devotion and wanted to kill him. Holica could not be harmed by fire. So she took Prahlad and sat in a huge fire with him in her lap. But the Lord protects His servants. Prahlad was untouched, while Holica was burnt to a cinder.
Holi festival originated when Prahlad's friends celebrated his devotion by showering each other with coloured paint. -- This celebration became a tradition.
In 1978 Holi was celebrated by Guru Maharaj Ji and His devotees in Malaga/Spain and in Miami Florida.