My reply: The exact color that is right for you depends on your skin tone even more than on your eye color. There are many beautiful purples, and plum is a great option, because as a warmer color than violet it's more flattering on most. The ones I'm listing here are my personal favorites:
Dior 2 Color Eyeshadow. You can't go wrong with Dior. The shadows are very pigmented, easy to apply, blend beautifully and last without fading and creasing. Diorart is a combination of a soft plum and medium/fair pink that complements it beautifully. For more drama, there are the new. They are bolder and more shimmery. Amber Plum has a golden sheen and would look lovely if you're looking for a warmer tone.
I've written before about Bourjois Petite Guide de Style. The tiny booklets are among my favorite makeup items of the season, and I find all the colors to be very wearable. Excellent quality and long wear make them a very attractive option. Coquette Rosette is a violet/pink combo. From my experience, the shimmer is very delicate and is office appropriate.
Lorac single shadows (as well as their palettes) are among the best around. They are never too shimmery, but the colors are true to to what you see in the little pots. Garnet is a rich plum, one that I would have bought for myself if I didn't own several others already (Diors and a couple of sadly discontinued Elizabeth Ardens).