Twelve colours for the maps with paired regions
This blanket represents a map of 24 paired regions; a couple of regions is identified by the same colour and, if we take any couple among the other 11, there's an element of the first couple that is adjacent of a region of the chosen one. We need 12 colours to colour the map in this way. In general, 12 colours are enough to colour every map with paired regions.
© matematita
The image belongs to the sections...:
Bags, baskets, ecc (Anthology of images)
Colouring a surface (Topology)
