I've gotten Vinca seeds from Swallowtail gardens for the past few years and they germinate wonderfully for me. I put them in a flat, saran wrap over that, and then newspaper over that as they need dark to germinate. Sometimes I start them on top of the upright freezer as it's warm. Once they germinate, I put them in a southern exposure window and they do fine.
They are also a re-seeding annual down here but they get started on their own much later than I like so I sow seeds as well.
The Pacifica series looks like it might have the color you're looking for.
https://www.swallowtailgardens...