Having Gone through all the phases of knowledge,loathe,irritation,observance, passive resistance, active participation and exhilaration, i can tell you this: This is as closest I've ever experienced the zombie apocalypse!
The symptoms look rather innocuous at first. People walking along corridors, smiling at each other, applying colors on each other. Perfectly alright.
The stage 2 looks a bit menacing. Some where, some one gets this idea that throwing people into the mud would be a great idea. And it spreads like wild fire! Before you know it, you are lifted into air, and plunged into the mud. you are dragged all over the place in the mud.
The final stage is sheer madness. People start tearing up each other's clothes. No, really. No mercy. No exceptions. People were stripped down to their bare minimums and the mayhem continues.
Apart from the phases of symptoms, another reason why i compare this to Zombie phenomena is the change in attitude you experience. You may hate Holi, you may loathe all the hoopla surrounding it, but once you were bitten, i,e were thrown into the mud pond, you will inexplicably engulfed by an urge to infect more victims. Without knowing, you will become the zombie you detested minutes back....
Of course, unlike the Zombie apocalypse, this lasts only till afternoon, and sanity prevails by the evening. But the muddy rooms, teared up clothes hanging from trees and the traces of color that refuses to be washed off will still remind you of the mayhem that ruled the morning!