Yes, you can make amaranth popcorn.
Trouble is, when things are hot enough for the amaranth to pop, things are also hot enough for it to turn black black black.
Or at least, that's what happens when I pop amaranth seed: pour a bit of oil into a pot, put onto a stove, heat, add a thin layer of amaranth seed, watch things pop -- oops, now put a lid on things as you notice how much is hopping out of that kettle.
Turn off the heat, take off the lid, and stir: there's lots of black seeds at the bottom.
Amaranth does make the tiniest cutest popcorns, but you really have to fish around to find the popped ones in among all the unpopped seeds.