Ah, finely one that I consider myself on expert on. There is no Yellow Van Buren. There is no Pink Van Buren. There is simply Van Buren. Grow it in the sun and you get yellow, grow it in the shade, you get pink. I have 5 Van Buren in the ground ALL taken on the same day. ALL from the same trunk. This one variety's colors are dependent on the sun. Mine have been in the ground 8 years and I've grown dozens of them for friends, collectors, and landscape jobs. I've taken yellow ones and put them in the shade and they end up pink after a year or two. Put the pink ones in the sun and after they go through some sunburn, they come back yellow.
And if anyone needs a Van Buren, the mother plant along with another 35 surrounds a pool enclosure, just east of here and you can take cuttings anytime you want.