That's what's known as a 'chase' kit. If I remember correctly, there was one per case in the 'chase' color, which varied from model to model. In the case of the Refit, it was blue, wheras the rest of the kits were white.
Yeah, I don't get the chase thing with a model. It's not like a diecast car where you can sit it on a shelf and display it in it's package. It was made to be assembled and painted, not displayed on it's sprue.