I don't think this is a reverse on the color. The photos will fool you in judging the size of the beans in relation to each other. The darker bean is a lot smaller than the Black & White bean, and I didn't find one single dark bean in the pods that produced the B&W bean. I've also never seen the B&W Goose ever put out an outcross before this year.
This Is another recent outcross discovered in my garden in 2012 called "Black Eyed Gem" (top photo). The seeds look somewhat similar to Magpie, but the seeds and pods are definitely wider and heavier. I grew this bean in 2013, 2014 and then again this year. This season "Black Eyed Gem" produced a brown version (bottom photo) that looks just like itself.
In 2014 Black Eyed Gem (which was shown yesterday) had produced three segregations. I called it Black Eyed Gem Segregation #3 (top photo). I decided to grow that segregation out this year and it produced one segregation of it's own (bottom photo).
Yes now that you mentioned that it does look a bit like Painted Pony. This seed is probably 1 and 1/2 times the size of PP.
I've been posting these beans in alphabetical order. Wait until we get to H and I post what has happened to my Holstein bean. We talked about it on emails before.