Your most useful information about this can be found in Geraldine Dahlke's Book of Patterned Pastes (see it here on Amazon) http://www.amazon.co.uk/Book-Patterned-Pastes-Cakes-Sugar/dp/190511... - plaid is doable, and is surprisingly easy to do, but hard to describe (unless you're Geraldine Dahlke!). But you need her instructions (which are very well illustrated) to guide you - there are so many patterns you can make. The general principle is laying various strips of paste together (according to the size and colour of the pattern you want), into a sort of sausage. Then you cut slices of your sausage and lay them together and roll your fondant - this causes the various colours to merge slightly giving you your pattern.