Do you want the triangles to be the same color as the hat or a different color? You could probably use a regular hat pattern, like this
one, and add some triangles with either reverse stockinette stitch or a second color.
If you have a multiple of eight stitches, this would make a triangle pattern (if you're knitting in the round). Just knit the K's and purl the P's (or use one color for the K's and another for the P's).