Combine dressing ingredients in food processor bowl and mix with steel knife until blended. Taste and adjust, if necessary. Set aside or chill for later. With 2 mm slicing disk on food processor, slice red cabbage. Transfer to collander, rinse and drain well to remove some of the red dye. With same disk, slice green cabbage. Transfer to large bowl. With small grating disk, grate carrots. Add to green cabbage. With steel knife and food processor running, drop scallions and process for a second or two. Add to bowl. Add drained red cabbage to bowl, toss well. Pour dressing over. Toss again and chill. Can be made 24 hours in advance. * - Two 8-ounce yogurt containers will yield about 1 cup drained for an hour or two.