Work this part of the scallop with C1. Orient the chain so that a row of non-overlapping loops of C2 is framed by C1.
Set up: Insert the right needle into the first C2 loop from back to front, then into the next C2 loop the same way. Place the left needle into the second C2 loop from front to back so the left needle is behind the right needle.
Create Stitch: Wrap C1 around the right needle back to front and pull through to create a stitch (this is a purl, not a knit). Keep C1 in front of the work.
PU Loop: Insert the right needle into the next C2 color loop on the chain from back to front then insert the left needel behind the right, into the same loop.
Repeat Create Stitch and PU Loop until there are 5 stitches on right needle (one will be an unworked loop), ending with Create Stitch.
BO 1 st. 4 stitches
Rep PU Loop and Create Stitch. 5 stitches
BO 2 stitches by pulling the second and third stitches over the end st. 3 stitches
Knit backwards: Move yarn to back of work. Insert left needle into the back of the first st on right needle and wrap C2 from back over top of left needle and pull the loop through. Repeat in remaining 2 stitches.
Move the yarn to the front and purl the 3 stitches.
Next Scallop: Pick up the two C2 loops as in Set up and repeat scallop.
Repeat for the correct number of scallops for a cap of the desired size.