It's possible that your black and white photo has turned discolored due to age or exposure to sunlight. Over time, the chemicals in the photograph can break down and cause the colors to shift. Additionally, if the photograph has been exposed to direct sunlight or high temperatures, the colors can fade or become discolored. Another possible reason for discoloration is damage to the photograph, such as scratches or water damage. It's also possible that the photo was printed with poor quality ink or paper, which can cause the colors to fade or become discolored over time. Finally, if the photograph has been stored in a humid environment, it may have developed mold or mildew, which can cause discoloration and damage to the image.