You need to prepare for the accent wrap when doing your primary wrap. Place a tie-off loop onto the blank BEFORE starting your main wrap, with the open loop facing AWAY from the guide foot. Proceed with the primary wrap as usual, moving the tie-off out of position after 5-6 wraps. After completing the primary wrap, you now have a tie-off loop in position for an accent wrap of a single or double revolution. Simply make a pass or two around the blank and then pull BOTH ends through the tie-off while gently nudging the accent band into position as the gap is closed. With a bit of practice and proper burnishing, it will look absolutely perfect.
Another way that is simple, which will allow for a three wrap accent. Tape the accent thread onto the blank BEFORE wrapping the primary wrap. Start your primary and after 15-20 turns, cut the tag end of the accent thread that is extending into the main wrap. Finish your main wrap and then go back to the accent thread that is taped. Immediately position a tie-off loop and make your three revolutions and pull through. You will find that three wraps holds when the other end has 15-20 turns. It will allow you to put a bit of extra tension onto the accent wrap, therefore keeping it in position.