These are all yellow coverts except for the rachis/halo and tiny little blue spots or smudges at the tip. They are mostly in the 4/0 to 5/0 hook size range. They are (and were) the feathers of choice for the May Queen wing. A pattern created by Maj John P Traherne, popularized by George M Kelson in the Fishing Gazette and immortalized by Paul Schmookler and Ingrid Sills in their First work The Salmon Flies of Maj John P Traherne published in 1993. May Queen is the fly in the background picture (page 61 of that book) above.