On the ground in Nepal the Holi festival actually takes place over several days. Some quoting as many days as fifteen. Though for most people they will only notice the final few days running up to the main day itself.Up in the remoter villages preparations are made, food cooked and various rituals performed in the weeks beforehand.
The first real noticeable difference I saw was that three days before Holi itself there is a tradition of throwing un-dyed water at women on the streets (Ill come back to that one). Then, two days later its colored water and dye throwing at everyone all morning on Holi day itself.
As you can imagine its a huge thrill for children as they prepare buckets of dye and fill up with water. Actually, there was a tradition of bringing Holi from places to places, so different places could have different dates for Holi celebration in order in olden days. In some part of India, this still holds true. Now, in Nepal there are only two days celebrations.
People used to make Pichkari (water guns) out of bamboo. And throw colored water on each other. Now-a-days balloons and plastic water guns (pichkari) are used. The balloon filled with water is called Lola in Nepali. Kids start throwing lolas on each other from week ahead of main Holi days.
People collects wood and burn fires and play music and performs dances. Some drink bhang and go crazy and make jokes.
The burning of the wood log in village and town avenues are very important part of Holi celebration. This event is called Holika Dahan, the end of Holika.
Holi is official holiday in Nepal. Offices are closed on Fagun Purnima days in hilly reason to celebrate Holi and the very next day, Terai is off for the celebration.