Bridges 2012 Regular Paper

In this paper I will investigate some properties of a special group of tilings. Namely those tiling's that can be coloured with only two different colours in such a way that every set of two tiles which have a common edge have a different colour. In the works of M.C. Escher these tiling's play an important role. In his book Regelmatige Vlakverdeling [1] M.C. Escher writes about the foreground-background phenomenon of this group of tilings. In fact these 2-colorable tilings can be seen as a compound of two groups of tiles. And so we can split a 2-colorable tiling in two sets of tiles and we can concentrate on only one of these sets.