I usually make my ruffle for my quilts about 2-1/2" to 3" finished. I have never worried about the width compared to the border (maybe I should have?)
I have thought about a 2 color ruffle, but I have never done that. I would make try a small strip - about 12" or sew and see how it looks. I was worried how the seam where the 2 colors were joined would look and lay.
If you do a 2 color ruffle please show how it turned out I would love to see