In a bag we have \(99\) red balls and \(99\) blue balls. We take balls from the bag, two balls at a time:
If the two balls are of the same colour, then we put in a red ball to the bag.
If the two balls are of different colour, we return a blue ball to the bag.
Regardless, after each step, one ball is lost from the bag, so eventually there will be only one ball. What is the colour of this last ball?