Here's a capture of each, in order of speaking appearance, or first close-up (although not necessarily from the scene in which they speak that first line!):
CLEON

SWAN

FOX

COCHISE

SNOW

REMBRANDT

COWBOY

VERMIN

AJAX











now that's a very plausible theory, as it always seemed odd to me that they'd go out of their way to add another fabric/color, and would account for why it seems lighterNinth Delegate wrote: ...one theory is that the vests might have been treated after the piping was added, and what we see in the diamonds is its original colour. Being die-cut, the studio lights can cast shadows and reflect light to make it appear a different colour.