You have a jar filled with marbles. some are orange and some are blue. you also have a supply of marbles of each color outside the jar. we carry out the following process. we reach in and pick two marbles out of the jar. if they are both orange we remove them and add a blue marble from our external supply of marbles. if they are both blue we put one back and remove the other. if one is blue and one is orange we put the orange one back and remove the blue one. we continue until there is only one marble left. what is the color of this last marble?