I don't know if it was still true at the time the photo was taken, but for a long time colours didn't register on plates with completely accurate tonal values - anything red or green came out a bit darker than in RL, and blue/yellow came out lighter*. I'd guess from the relatively deep shades of gray that the waistcoat in question was some sort of red/green checks.


* This remained a problem in the early days of cinema - anyone with blue eyes looked all creepy. Hence no blonde movie stars until much later.