Derived from the inventive Serpentine method (described and illustrated with many examples) in Chapter 3 of Cecelia Campochiaro's Sequence Knitting (2015). Row 1 is the basic sequence. If knit in a single color, this is actually a 5-row pattern, likewise reversible. To work with 2 colors as shown: CO with A (blue); work rows 1-2 with B (green), 3-4 with A, etc. First 10 rows end with B; next 10 with A. When changing color, bring the new one over the one being dropped, or otherwise handle edge consistently.
Shown with a cast-on count of 22 stitches.