I always assumed Yoshi was red and white. When Yoshi was younger, he had a TINY bit of black on his back, along his spine. As he got older, the black became more noticeable. I'm wondering if he's actually he's sable? or something else? I'm not sure. Not that it matters, of course, just wanted some opinions. Hope you can see what I mean by these pictures.
Jack similarly has sprinklings of black-tipped hairs, more prominent when he's out-of-coat. I had a topic on it many moons ago (and yes, he's since lost about 8 pounds so I feel guilty about the pictures!).
After that topic, we visited with a show breeder, looking at one of her adults she was rehoming. We ended up not bringing home Becky, but the breeder said with full confidence that Jack is a red-and-white, with some sabling. So, not a sable at all. I'm not sure where the dividing line is, but as someone else mentioned in my old thread, I think they need more distinctive markings on their side and the black cap on their head to be considered sable.
The breeder who saw him in person and declared him red-and-white has done some judging and had BOB at one of the recent National Specialties, so I kind of ended up trusting her call in the end. I now refer to him as red-and-white.
http://www.pwcca.org/colors_SW.html refers to the distinctive "widow's peak".