I don't see hou you could be getting color from the sabots Pluckit. I've shot all kinds of sabots, red, green, blue, orange. Never got sabot color on a patch.

A day after I cleaned my .32 Pedersoli I get patches with light rust color like that, even though I flushed it well and oiled it. Just for the heck of it, I ran a very wet patch of Liquid Wrench down the bore and let it sit for a couple of hours. Then I started patching with dry white patches. They came out a little darker than the one in your picture, but after about five patches they were coming out pretty clean. Then I ran a very wet LW patch again and let it sit. Darn if the first patch didn't come out rust colored again. But after three or four more dry patches there was no more sign of brown.