You can retrieve the correct Integer from the prefecence list1
Integer values = getPrefs.getInt("list1", 2);
then you could switch from the values retrieved:
switch(values ) {
case 1:
tp.setColor(Color.RED);
break;
case 2:
tp.setColor(Color.GREEN);
break;
case 3:
tp.setColor(Color.BLUE);
break;
case 4:
tp.setColor(Color.YELLOW);
break;
default:
tp.setColor(Color.GREEN);
}