In 82 rosewood metallic was a standard color option. I agree it was definitely more brown that the current color of your car. As the copy of the window sticker has Rosewood Metallic listed I would assume your car came in the standard Rosewood Metallic color. If your car was anything other than the standard color it would be listed as code 98 or 99 "color to sample". I highly suspect yours has been repainted.
Here is a link to the Porsche Classic color sample card.