Ray the dubbing came off the most yellow part of the piece of tanned Marten hide I have (probably part of a coat collar).
IMGP0168 by
William Lovelace, on Flickr
I suspect the belly fur would have been more appropriate for the fly. The tips of the fur are yellow but the roots fade to a creamy tan.My dubbing looks more of a tan when blended but lightly dubbed on the silk the eye (and camera) is fooled into seeing something more in line with the idea from the original.
Here is the text from Herd's book
Trout Fly Patterns 1496-1916 the History of flyfishing Volume Two
Pale Yellow Dun
Wings: The lightest part of a feather from a young starling's wing.
Body:Yellow Mohair, or martin's pale yellow fur, tied with yellow silk.
Hook: No. 12