"An Analysis of Judith Baker's Pixilation Study," by Zach Jendro and Trish Fleming supports the idea that the arm belongs to a spectator on the sidewalk or on the Elm St extension mini-street in front of the TSBD.
I contributed an image for this article. Also, another older image of mine was used.
There are people who just won't get it and try to keep this a mystery, or insist that their false, subjective impression is a fact when it isn't. And people are just trapped, conditioned through years of lies to see this part of the Altgens photograph only within the context of the question who is "Doorman?" Is "Doorman," Oswald or Lovelady, when the arm doesn't belong to "Doorman," at all.
One such example is Charles Cliff:
First of all, there was a Black man standing there.
Second, it's a different Black man than the one seen in profile at the bottom of the steps below Lovelady, who may or may not be Roy Lewis.
Third, to declare that that Black man seen in profile is not really there at all and that what people mistake for a Black man standing in profile is actually "an optical illusion," created by Lovelady's shirt shows you how desperate some people are in creating falsehoods and mysteries rather than using logic, science, and common sense to ascertain the truth.
Charles Cliff elaborates further in what he claims he sees based upon this false colorization version of the Altgens photo.
Stereoscopic viewing of a copy of the Altgens photo, which you can get from the AP, is a very valuable tool. I don't think it can be done at all in the scanned, digitized world of websites. It is old school, looking at a real photograph.
Colorization merely colorizes what the person doing the colorizing wants colored. The person doing the colorization is the one picking which color, and where to place them. It is not objective at all. It's quite possible none of the colors are correct, neither for clothing or skin color.