This is perfectly Normal.
Flabébé and Floette can hold five different-colored flowers based on the color of the flower bed they were caught in: red, blue, yellow, white, and orange. When Floette evolves into Florges, it maintains that color flower. The color of the flower cannot be changed.
Apparently White and Blue Flabebe are the only forms of Flabebe that can be found in the Purple Flower Bed because of the fact that if you mix a certain percentage of Blue with a certain percentage of White you can create Purple. Hope this helped :)