To add, natural furs aren't just one consistent color the way synthetics are. There was a tier back in the day, John Atherton, who was also an artist (painter) he used natural dubbing and hackled his flies for just that reason. Insects being natural aren't just one color. A "gray" mayfly is actually a multitude of shades that give an overall impression of "gray". Makes total sense to me. "John Atherton (1900 – 1952) was an artist by trade and incorporated his impressionistic art into the flies he tied. "
Not to hijack the thread but here's a bit about John Atherton (click on the grey box to see the flies if they don't show)