Red flowers. According to the mathematical equation, the number of yellow flowerpots is X, the number of blue flowerpots is Y, and the number of red flowerpots is 2. We can get the rule that every two adjacent flowerpots have different colors, and one flowerpot and the next flowerpot have the same color. The sequence is yellow, blue, red, yellow, blue, red, yellow, blue, red, yellow, blue, red, yellow, red, blue and red, that is, the last pot is safflower.