Apparently, this isn't a true native, but cultivated to be yellow. According to American Meadows, "Hello Yellow Butterfly Weed was developed from the native Butterfly Weed and has golden clusters of flowers."
A local vegetable breeder, Ken Ettlinger, considered the range of colors exciting. Our plants ended up ranging in color from a brilliant peachy salmon to pale orange to yellow. Ken explained, "You're growing out a specialized variety, and the monarchs will still come to feed on them." So I selected for the colors I liked and clipped the yellow so the bees couldn't cross pollinate them.
Then Dai Dayton from Friends of Long Pond Greenbelt said, "We can't buy Quality Parks butterfly milkweed if it's not truly native, because Vineyard Field is a grassland restoration, and we need it to be orange." Fortunately, most of the hybridization had disappeared, as I was bringing in more seeds from other sources to maintain biodiversity. I then assured her that they were the traditional orange.