The first example above is the Campbell tartan, often sold as "Ancient Campbell" by vendors. It is the same sett, although in a lighter shade, as Black Watch, a regiment raised by the Duke of Argyll in 1739. All Campbells and septs may wear this sett.    Look carefully, and note that it is a double sett. This means that it takes twice the distance to repeat the pattern as a single sett, or a basic square pattern. Look at the double tramlines, pairs of narrow black lines like railroad tracks. Moving across the tartan left to right, there is one double tramline in an area of blue, an area of green with a single line, an area of blue with two double tramlines, followed by an area of green with a single line. This completes the pattern, which is the same up and down as it is across.    Hues may vary according to preference, as long as the colors are blue, black and green. Color schemes sold by the mills are usually called "ancient" and "modern." These indicate a lighter shade for "ancient" tartans, purported to represent the lighter coloring of the older, traditional, methods of dying the wool. The "modern" tartans are darker, with blues appearing to be verging on purple. So, if one chose to wear a lighter shade of Campbell tartan, one would order a kilt made of Ancient Campbell tartan in the "ancient" color scheme.    This tartan is worn by Campbells originating in Argyll, as well as any other member of Clan Campbell. This is the main tartan of the clan, and may be worn by all Campbells and those with Clan Campbell sept names.