All @LACityPets are offering reduced adoption fees on primarily black animals. Black animals are often overlooked because they’re stereotyped as aggressive. Couldn’t be further from the truth. https://t.co/Os1kd9etKP— Alanna Rizzo (@alannarizzo) September 21, 2019
Here's the Wikipedia page on "Black dog syndrome":
The proposed phenomenon may be due to a number of factors. Research has identified geographic location, fear stigma against certain breed types, and the fact that large, black dogs are often portrayed as aggressive in film and on television as possible correlates. Initial research at one location identified a longer period experienced by black dogs before adoption, but subsequent studies considered to be more robust (as conducted in a larger number of geographically spread shelters) has shown that when shelter visitors video-recorded their walk through the adoption area, they spent equal amounts of time looking at every dog, regardless of coat color. Other studies have suggested brindle dogs may be more likely to experience longer delays before adoption than black dogs. Coat color bias seems evident, but may change depending on geographic location.
Some people believe that during the pet adoption process some potential owners associate the color black with evil or misfortune (similar to the common superstition surrounding black cats), and this bias transfers over to their choice of dog. Additionally, many shelters feature photo profiles of their dogs on the shelter website. Because black dogs do not photograph well, lighter-colored dogs have an advantage with potential adopters browsing the site. A study done by the Los Angeles Animal Services challenges some of these claims, saying that a full 28% of adopted dogs are black. However, the bias theory simply asserts that predominantly dark animals take longer to be adopted than their lighter counterparts, and that large dogs take longer to adopt than small ones.
However, appearance in general does play a role in potential adopters' selection of shelter dogs. In a 2011 study by the ASPCA, appearance was the most frequently cited reason for adopters of both puppies (29 percent) and adult dogs (26 percent).