Hong Kong’s police force introduced a new weapon in their arsenal over the weekend, colorful water cannons.

The water cannon was deployed on Saturday against protesters who ignored a police ban on demonstrating. Rather than your standard H2O, the water shooting out of the cannons was infused with blue dye, assumably to help make identifying suspects easier for police.

BREAKING: Hong Kong Police for the first time deployed water cannons infused with blue dye. The idea is to identify protesters and facilitate arrests. Carrie Lam reportedly told her cabinet that she would “lock them all up.” Looks like she meant what she said. pic.twitter.com/N10HzNggk8 — Jason Y. Ng (@jasonyng) August 31, 2019

Hong Kong protestors are now being sprayed with blue-dye water cannons so police can make arrests pic.twitter.com/yfvFRmj4Mz — NowThis (@nowthisnews) September 1, 2019

Some have called for Hong Kong’s protester to start painting themselves blue in defiance of this latest innovation in police tech. While an army of Smurfs has yet to emerge, people have at least taken to leaving around changes of clothing in metro stations to help those who have been dyed.

Ppl leaving a change of clothes for protesters in MTR stations, in case they were dyed blue by water cannons. That’s the support behind the movement, always has been. Not mysterious foreign forces, just plain old Hong Kong sympathy and kindness.#StandwithHK #hkprotest pic.twitter.com/xSH0rqnCJb — Denise Ho (HOCC) (@hoccgoomusic) August 31, 2019