Perhaps you could use more than one color. Use a soft green on the purple and a color of purple on the green. Consider using 40/3 thread such as Superior's King Tut or Sulky. Maybe even variegated threads. Your quilt will be very pretty. Simple quilting will be very pretty. Curves using your hopping foot or walking foot would be very pretty and very complementary. Please do not meander as it would be distracting from the lovely organized curves in your blocks.