Frank,
I don't have a definitive answer for your question, but I can say that I've made the same observation that you have, in that the use of the tri-color ribbon seems to be spreading. I can't recall exactly, but I noticed this happening with increasing frequency maybe 4-5 yrs ago in photos of new award recipients (probably from Chechnya, etc), as the brightly colored ribbons really seemed to jump out in the photos. Realize this isn't too much help to you, but thought the timeframe might help your researching...