Heh, good luck. There are so many similar shades, variations, and potential for fading and discoloring that it's hard to be sure a ribbon is correct unless you opened the pony yourself. That said, there is a pretty good site showing the ribbons MIP, though it's sadly incomplete. It'll be useful for IDing, though, but with it being online there's no guarantee that you'll be able to distinguish between similar shades.
https://mylittleponyaccessories.weebly.com/information.htmlAs for the ribbon in question, it could belong to a number of ponies, including Bonnie Bonnets, SS Fifi, Li'l Sweetcake, Speedy, and others. Compare it to that of Dancing Butterflies and take a picture; it'll help to know how much the shade differs. If somebody has a confirmed Dancing Butterflies ribbon and a ribbon to compare, they can make suggestions.
I, unfortunately, cannot contribute any more. I only have one genuine pony ribbon, a pale blue one, and I don't know whom it belongs to. It was my mother's and only fell into my possession since it got mixed in with her Barbie stuff. Currently, my Tricky Tails is wearing it. It looks cute on her!