Today's square is a grid pattern:
Row 1 - chain 21
Row 2 - dc in the 2nd stitch, work 3 more dc in the next 4 ch, change colour by working the last part of the dc with the new colour, work 4 dc in the new colour, carry the first colour along the row, repeat to the end.
Row 3&4 - repeat row 2.
Row 5 - repeat row two but using the second colour to start the row to create the second set of squares.
Continue in the same manner until square.