Regarding ancient, modern, and weathered tartans, sometimes the whole thread pattern changes, and sometimes only the thread colors change, like to more muted or pastel colors. Ancient dyes are supposed to more closely represent what the tartan would have looked like before more colorful wool dyes were widely available, but currently most clans recognize the modern tartan as the official tartan. For a more in depth answer, check out our blog post on which tartan you should wear.