These are knife pleats. You’ll be able to see that more clearly when the kilt is finished and pressed. A teal strip is in the center of each pleat. Choosing this stripe highlights the purplish blocks that border it. This is my third kilt in this tartan. Each one is pleated to a different element, so each one has its own look. I’ll post a comparison later on.
Kilt progress: Three pleats done. Tape measure is sticking out of the “buttonhole” opening where the strap will go when it is worn.