Alternating cable cast-on 148 stitches for 2x2 corrugated rib. Set-up round is with color A (background, held in right hand, knit all stitches), to be followed with two-color stranded knit in K2P2 rib, 12 rounds/ 1& 1/4 inches.
Increase two stitches in first pattern row to make 150 (multiple of 50 stitch pattern). Purl one round with A then follow chart. Add a purl round after round 15.

started with 15 g unknown navy blue for color A.

After three chart repeats I topped the hat in a method of Rox Rocks. Twenty-two rows for the decrease sections.
Kept two colors throughout with some manipulation of the pattern.