Just to recap (on my scattered posts on Manipur's 5 day Holi celebration - Yaoshang)
Holika dahan is celebrated on the day before Holi to symbolize Lord Vishnu killing the demon Holika by burning her to save his no. 1 devotee prahlad. The manipuris put up temp huts and burn it after a puja.
The first celebration on the day of Holi begins in Lord Krishna temples for it is after all Krishna's festival.
The next days go by where young and old go door to door to perform dol jatra and collect donations for the local community's sports meet, moonlit evening dance events and general merriment.