They all are pretty IMO. I'd decide based on my skintone and what I already have. If it was me, I'd go for the navy because I have a lot of purple already. Just an example.
Oooh...these are so Glamorous! They remind me of Marylin Monroe...I think the Purple is most beautiful, but I am a complete Purple Freak...If you can, purchase all 3!
You can always return one if you decide you aren't happy.
i like the gray..if your going to do something nice with your hair and makeup..purple if your trying to keep it looking glam but dont want to do much with your makeup and hair..black if you want to play it safe.