From The Boston Guardian

Some South End lintels in the Ellis and Eight Streets sections of the neighborhood may still bear the signs of their lurid pasts.

In the late 1940s, fed up with johns knocking on their doors in search of prostitutes, residents came to an agreement with the area’s brothels that they would paint their first-floor lintels.

“They had to go to the bordellos and ask them to do it,” said Paul Duffy, longtime neighborhood resident, who was a little boy at the time.

“I think at that time {the paint} might have been red and turned salmon or pink.”

According to Duffy, there are still some buildings that have the mark from the past, but he could not name specific addresses.

Historians reached for more information were not familiar with the paint markings but provided details about South End prostitution half a century earlier.

“[The South End] became very active with brothels between 1890 and 1910,” said Mary Beaudry, chair of Boston University’s Archeology Department. “The johns were just about everybody.”’

Here’s the whole article.