Yarns and colours
The choice of yarns is entirely up to you. If you are making nothing but individual squares which you stitch together later you do not need to use the same thickness of yarn throughout. Work to a template of your chosen size and the squares will all be the same size.
If you are picking up stitches to build onto an existing shape the yarns must be approximately the same thickness or the simple calculations will not work.
Modular designs are ideal for using up oddments of yarn. They also have the advantage that slight differences in dye lots will not be noticeable. It is possible to create a design using just one colour as the differences in the direction of the knitting will create interesting texture effects. Designs with two or three colours are common.
This staggered design needs three colours if no areas of the same colour are to touch
A checkerboard design needs only two colours
No design ever needs more than four colours but you may choose to use many more.
When you have two colours you can make two different arrangements (although you might argue that this is the same pattern turned round).
Arrangement of colours
When you add a third square it can go behind, between, or in front of the existing squares, making a total of six possible combinations.
If a fourth colour is added, it can go in any of four positions, in each of the six existing patterns -
If you were to add another colour there would be 120 possible permutations. Six colours would give 720 choices.
See Second Thoughts Pages 108 -