Echinocereus reichenbachii var. burrensis
Echinocereus reichenbachii var. burrensis is from Sierra del Carmen range in Mexico near Big Bend, TX. These have been cold hardy in our garden taking -17F and surviving other local gardens as well. These vary from the typical forms in having rusty red or brown spines. These still get the large Pink flowers that the others get.
I do not guarantee these in a zone 5/6/7 because everyones growing conditions are different but this would be a good trial plant to grow in your cold outdoor garden. Try to plant outdoor 90 days before 1st hard freeze.