Looks like Fair-Isle but it is all worked in slip stitch!

This jacket, knitted in a beautiful silk-blend yarn, showcases traditional slip stitch in a very unexpected way. the allover slip-stitch pattern enables you to work a Fair-Isle-looking pattern without any stranded work, making your stitching even and beautiful.

The jacket is worked in a seamless construction to underarms, then each front and back are finished separately and joined at shoulder seam. Similarly, the sleeves are worked in the round to underarms, and sleeve caps are finished in rows.