Quoted from Rasavage:
To me, the 6 color changers in BM66 make sense in the context of the game rules. However, I'm not sure whether that is a product of adding an element to the game, or working around cost limitation.
It's cost cutting. Putting the color changers in allows for you to take advantage of them later via code updates. They could have left them white in early code and worked towards improving the light show later. By putting the non-color changers in from day one, it shows that they had no plan to invest the time or spend the minimal extra cost. I think Ghostbusters has a great light show, but I really wish all the inserts were RGB.