The speaker imagines his love riding off into the sunrise, colors flying. (Oh, did we mention that she's riding a horse?) What else would you expect from a true romantic? To be honest, not much else happens in this poem. The speaker's love goes out for a ride and, like any obsessive person in love, our speaker spends time—lots of time—thinking about just how his love looks while she's out on her horse.
But as the poem continues, things get just a bit creepier. See, the lady in question is out on a hunt. And as she hunts, the language used to describe her, her horse, and her hounds gets more and more creepy. And then, well, bang. It turns out that she does manage to hunt something down—our speaker's heart. Ouch.