I liked this modular when I first saw it and knew that it would look wonderful in colour:

An interesting elbow bend, tubular construction and odd folding in fifths make this model interesting to make

You start with a split A4 page, box pleat and lock the tube, then slide one inside the other to make a rectangular hoopy thing, then nest another inside that one, then lock a third over the top of that one and you end up with a lovely sort of impossible looking shape

I like this a lot, the illusion of intersecting shapes in well designed and although a little time consuming it is satisfying and a keeper I think.