A couple of subjects require folding striped or spotted patterns. Professional origami designers solve such challenges by alternating the two (different coloured) sides of the paper. Neat examples can be found among several models of John Montroll and Marc Kirschenbaum, as well as others' works (a couple of these are shown in the gallery).
I met the first major challenge in this field while creating the origami version of the Hungarian Coat of Arms (see in the gallery). I wanted to fold the series of stripes on left side of the shield in a "clean" way: making regular parallel stripes, without disturbing edges. Moreover, I wanted to fold the double cross of the other side using the same sheet of paper. The task was way more complicated than any other before, but finally I managed to accomplish these goals almost entirely (the double cross has some extra edges).
A few years later I returned to the topic of folding regular stripes and managed to find a relatively simple algorithm of "extracting" any number of even and odd stripes from one sheet of paper. The algorithm is presented below.
The diagrams below are free to download for personal use only.
In all other cases my permission is required.