In Black

In black = in darkness?
Or
In black = in black dress?
Context:
　On April 15, many people were in the parks to

celebrate the former president birthday.
It was nice to see some real life, with dances,

lunches, and even alcohool.
For once, north koreans looked humans and did not

act like the robots they seem to be when you see

them walking in black in the streets.
Pyongyang North Korea