Round 1: Ch 3, work 2 dc in ring, ch 1.
(the ch 3 at the beginning is counted as a dc, the ch 1 makes a space)
* 3 dc in ring, ch 1
Repeat from * twice, join last ch 1 to top of starting ch with a ss.
End first colour.

Round 3:
With right side facing, join third colour with a ss in any ch-1 space.
Ch 3, 2 dc, ch 1, 3 dc in same sp
* 3 dc in next sp along side
in next corner ch-1 sp work 3 dc, ch 1, 3 dc in same sp
Repeat from * twice
3 dc in next side space, join with ss to to top of starting ch.
End third colour.

Round 4:
With right side facing, join fourth colour in any corner sp
Ch 3, 2 dc, ch 1, 3 dc in same sp
3 dc in each sp along side
in next corner ch-1 sp work 3 dc, ch 1, 3 dc in same sp
Continue in pattern around.
At end, join with a sl st to top of starting ch of round.

Round 5:
With right side facing, join fifth colour in any corner sp and repeat Round 4.

The fifth round makes the solid colour between squares so each granny square usually has the same colour for the last round.

You can make your squares as large as you wish by adding rounds continuing in the pattern.