The first rifle I stocked was from a blank of Am. black from Johnson. As for manure affecting the color of walnut, I call bullsh!t on that one!
(And for MP's of the future, it was a .270 on a Polish Radom Mauser action with an angled ebony forend tip and never got checkered. I did all the conversion work to the military action, stocked it from the blank, turned the barrel contour from a blank, fitted and chambered it as my first project at TSJC. I sold it in Springfield, OR (1985?) to get enough money to fly to Vegas and join the ACGG as a muzzleloading gunmaker. When I got there I was the only guy with muzzleloaders, everyone else was showing Mausers!)