I have a couple lilac trees in my yard that I've turned pens from. It's a very nice easy turning wood with lots of character. One problem is it cracks a lot when drying so if you haven't sealed the ends yets, I would do so soon. It has a tendency to crack spirally around the limb, making it hard to get usable pieces. The purple will really stand out against that light sap wood. Good luck!
Upon closer look, looks like you have the sealer part covered. lol Looking forward to seeing a finished pen posted when you get one done.