The Four Colour Theorem tells us that to colour any map such that no two neighbouring regions are the same colour requires no more than four colours. However, this rule does not apply to maps drawn on surfaces of different shapes. For example, how many colours are required on a torus (donut)?

If a map contains seven regions, and each is a neighbour of the other six, then seven colours are necessary to colour the map. Does such a map exist on a torus? This crocheted torus shows that it does! In fact, on a torus, seven colours suffice to colour any map.

Pattern Notes:

• Construct 7 rectangles 30 stitches wide and 9 rows high. Each rectangle measures 18cm x 5cm.
• Place the rectangles in a staggered diagonal configuration (see photos) and sew the long sides together.
• Finally, join the remaining edges so that they form a torus where each rectangle is joined to the other six rectangles. (This can be a bit fiddly.)

Other Patterns:
Here are some other 7-coloured torus patterns on Ravelry.

• Seven-Color Torus (Ungar-Leech Map) by Susan Goldstine, Sophie Sommer, and Ellie Baker.

• Seven-Colored Torus by sarah-marie belcastro and Carolyn Yackel.