For the slaw: Toss the jicama with the scallions, carrots, bell pepper and cabbage. Season with salt and pepper.
For the dressing: In a small mixing bowl, whisk the vinegar, lime juice, cilantro, honey, chili powder and cumin. Slowly whisk in the olive oil until the dressing is emulsified.
Toss the dressing with the slaw and garnish with additional cilantro before serving, if desired. Allow the slaw to chill for at least 30 minutes to allow the flavors to develop, or chill up to 2 days in the refrigerator.