Great Britain 356c is the Wilding 2d Queen Elizabeth with graphite line on back. I find mention of a Light Red Brown in my catalogues, but the left stamp is bothering me a bit. I'm thinking sunlight fading, but look forward to your comments.
Left stamp is the probable faded stamp (Mint, full gum on back)
Middle stamp is a "normal" color (Mint, hinge mark)
Right is a scan of another "normal" back. All three stamps have line on right side when viewed from back.