Gunpowder and/or Soot on bloodstained garments can be visualized by:

Gunshot residue on multicoloured, dark or blood stained cloth can be detected by infrared photography. Gunshot residue on light clothing can be seen as a smudge or smear. In many cases soot and gunpowder grains are readily seen on the clothing, indicating a close range shot. Sometimes examination with the naked eye and the dissection microscope is insufficient. Thus in heavy bloodstained garments, one may have to use Infrared Photography to demonstrate the soot pattern. Ref: Howdunit Forensics: A Guide for Writers By D. P. Lyle, Page 354; Concise Textbook Of Forensic Medicine & Toxicology By Sharma, Page 89; The essentials of forensic medicine and toxicology, By Reddy, 27th Edition, Page 203