"As flashpoints erupt between protesters and police in Hong Kong, water cannons filled with blue dye are being turned on the protesters. Hong Kong citizens were out en masse protesting for the thirteenth week in a row on Saturday, despite a police ban on rallying. The protests were sparked in June by a proposed extradition bill by mainland China..."
https://www.insider.com/hong-kong-police-fire-blue-dye-water-cannons-2019-8