We had quite a long discussion about striped stockings on my pirate mail list. The verdict was, as I recall - no, they are not accurate. There's not really much evidence to support their use/existence during the "Golden Age of Piracy."
Also, fwiw, the mass produced re-enactor stockings available today are constructed differently than those of the 300 years ago. I'd tell you more, but I'm just a simple pirate... with a friend who is really keen on period stockings.