In a sequence of adjectives, the general order is opinion, size, age, shape, color, origin, material, and purpose. Based on this order, "blue" (color) should come before "large" (size) since color typically comes after size in the sequence.
So, the correct order for your adjectives would be: "large" (size) followed by "blue" (color) and then "six" (number) and "American" (origin).
If you need to choose which adjective should come first, it would be "large" since it describes size and comes before color according to the typical adjective order.