How would a graph of negative and positive acceleration differ?

This depends on what the graph represents. If it is a graph of velocity on the vertical and time on the horizontal, then if acceleration is at a constant rate, the graph will be a straight line with positive slope (pointing 'up'). If acceleration stops, then the graph will be a horizontal line (zero acceleration or deceleration). If it is deceleration (negative acceleration), then the graph will have negative slope (pointing down).