You must have seen photos of protesters being doused with colored-water cannons by the police.
Simple: to identify and arrest them later.
Many water cannons on the market today come with a tank specially designed to store a semi-permanent colored dye.
The headquarters, along with the historic and white-painted Old Town House, were doused with purple.
In Uganda last year pink dye was employed to humiliate protesters.
In Israel, Palestinian rioters were sprayed deep blue, the colour of the Israeli flag.
The Hungarian police use green, the Koreans orange.
Indian police is particularly fond of purple.
(James Akena / Reuters)
Police spray Ugandan opposition party leaders with colored water during demonstrations in Kampala.
(Fayaz Kabli / Reuters)
Sources:1,2,3
