How Holi is actually played
Holi falls on the full moon of Phalguna, in February or March, and runs over two days. The first evening is Holika Dahan, a bonfire. The colour is the following morning — Rangwali Holi — and it is played in the street, in courtyards and on rooftops, with dry powder smeared on the face and thrown by the handful, and water added through pichkari and balloons as the morning goes on.
That pattern is what a colour has to survive. It is handled by wet hands, mixed with water halfway through, worn for several hours and then washed off. A powder that clumps once damp, or that sets into fabric after an hour in the sun, fails on the day rather than in a lab.