As spawning time approaches – autumn or very early winter in most rivers, though in some late-run streams salmon may spawn as late as January or February – the hen's colouration becomes first a matt-pewter and then a drab dark brown-grey. The cock fish, in contrast, begins to gain some brighter colours.
2005, Roderick Sutterby, Malcolm Greenhalgh, “Life in the Nursery”, in Atlantic Salmon: An Illustrated Natural History, Mechanicsburg, PA: Stackpole Books, page 21