Afraid I have to side with yodap on this one. There is no way there are manufacturing variations from dial to dial and I can't imagine that they would make such a minute change for one colour and not the others. Given the light spectrum each is reflecting it makes sense that the white is going to be more pronounced. Since it is reflecting all visible wavelengths of light (400nm ~ 700nm) the white is going to seem very bright where as the blue is only reflecting about 400nm~500nm spectrum giving it a less brilliant appearance. These differences in amount of light reflected will make one, the brighter one, seem larger than the other. An example of this is in how our eye perceives lume, especially in the dark. A watch with average rep lume will appear much sharper and smaller than the same watch with say C1. The glow tends to fuzz the edges and make the object appear larger to the eye. Same thing with white dial vs. a solid colour.
Just my 2 cents