I thought this was a milkweed bug, but the description is for east of the Rockies. There are many of these insects on the milkweed plants and many are mating.
Bordered plant bug?
Length 6 mm.
2 light grey and 1 muddy brown.
Hemiptera /hɛˈmɪptərə/ is an order of insects most often known as the true bugs (cf. bug), comprising around 50,000–80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others. They range in size from 1 mm (0.04 in) to around 15 cm (6 in), and share a common arrangement of sucking mouthparts. Sometimes, the name true bugs is applied more narrowly still to insects of the suborder Heteroptera only.