The James Sewell Ballet offers up a fall season as brisk and multi-hued as a cascade of autumn leaves. The concert leads off with Sewell’s new “Octet,” set to Mendelssohn’s Octet for Strings in E-flat, written when he was 16 years old. Eight dancers spring, soar, and test the limits of form and physicality to music played live by the St. Paul Chamber Orchestra. For the second half, JSB partners with McKnight International Choreographers Sharon Eyal and Gai Behar of Israel. Their work, “Killer Pig,” inhabits an entirely different realm of expression. At a recent rehearsal, dancers laid down a mosaic of moods, from street-wise urban to sly and sensuous. Fast-paced, witty, and stylistically diverse, “Killer Pig” allows the terrific JSB dancers to get down and embrace both their balletic virtuosity and their wild side.