Madelina has a bag of colored cubes. She has 16 red cubes, 4 blue cubes, 8 green cubes, and 20 yellow cubes. She adds 4 red cubes to the bag. How many of each of the other colors would she need to add to keep the probability of randomly selecting 1 cube of each color the same as it was before she added the cubes? Justify your response.