If the dragon has no felt pad on the bottom, and has a Windstone stamp, it originally was brown or green. If there is no Windstone stamp I suppose it is possible that the felt has been removed.
Or, as you probably know, there have been knock-off versions of Windstone dragons over the years. They usually are resin rather than gypsum and often the eyes are part of the cast rather than glass eyes. I’m guessing that you can tell whether this dragon is original or a knock-off?