If you had a chance to look deeper around Jakarta, you might occasionally see a Bendera Kuning or a yellow flag mounted on a side street. Yellow flag in Jakarta and West Java is known as a marker of a person’s death
As quoted from Kompas, the story of the yellow flag began in the VOC administration. During that time in Batavia and surrounding, there were outbreaks of deadly infectious diseases. VOC administration uses a yellow flag to mark homes or places of people affected by the deadly disease. The Yellow Line is the rectangular flag with the letter Q or quarantine. The surrounding population was forbidden to come closer to the house to prevent disease transmission.
People whose homes were marked with yellow flags eventually died. Since then, the yellow flag is widespread to mark a person’s death
Note: Picture is taken from here