This is a photo of Jewish women from Subcarpathian Rus who have been selected for forced labor at Auschwitz-Birkenau, march toward their barracks after disinfection and headshaving (source, probably appearing in this book).
One of these women is my grandmother (marked here) who is celebrating her 86th birthday soon.
/u/Eclectix did an amazing job of cleaning up and colorizing the photo.
Not only did he do a professional job on the technical side, he also did some research to be as accurate as possible:
I’ve been researching the clothing worn in the camp, and it seems that grey is pretty much the predominant color, with the major exception being the head coverings which belonged to the people who wore them, and were usually white, grey, or brown.
I have eased out the grain as far as I can without doing real harm to the photograph. I particularly softened the grain in the shadows, where it was most noticeable and the details less essential. I added a sky with light cloud cover, as the day is obviously bright as revealed by the hard shadows present. The last thing I did was adjust the levels to increase the overall sharpness and contrast.
In addition to general restoration and colorization, I also brightened up your grandmother’s face just a tad to make it more visible. I hope you and your grandmother both enjoy the picture.