Hmmm. The 42nd wore the Government tartan, usually referred to as "Black Watch" these days, which was also worn by the 93rd except in slightly brighter shades. So, dark blue, with middle green striping, and a thin black overstripe down the middle of the green stripes. That works in this scale. You can use slightly lighter shades for the 93rd if you think it will distinguish them from the 42nd, but the facing colors will be the main difference (yellow versus dark blue).
The 71st wore what is now called the MacKenzie, or Seaforth sett. Starts off like the Government tartan but with a thin white overstripe over the green stripes and a thin red overstripe over the blue, between every other set of green stripes.
72nd wore Prince Charles Edward Stuart tartan trews and that's a complicated sett. I have done it but it requires a scarlet base, then dark blue stripes and a series of thin yellow and white overstripes. Very difficult to describe in words, you should look up the tartan in a book or online and check how other painters have replicated it.
79th wore a unique tartan, Cameron of Erracht, that is NOT based on the Government/42nd tartan. I start with a base of dark green, then dark blue stripes, then a series of dark red overstripes thinly spaced, followed by a thin overstripe of yellow ochre. This is another one that's difficult to describe in text.
I'll attach some images from my collection here in case it's useful; these soldiers are from different periods, but this is how I have done some of these tartans in 25mm scale. Nothing from the 71st cause I haven't painted that complete combat unit, only individuals in that tartan.
42nd / Black Watch
79th / Camerons
72nd / Albany's
93rd / Argyll & Sutherland Highlanders
finally dips his toe into the world of Aeronef.
