Envy? Sorry, I couldn't resist!

I don't know the exact reason for this (other than it's probably normal for some species/cultivars), but many junipers seem to lose their blue bloom as they mature. Chemical use, excess fertilization, and other things that WE do might cause this, too.

Does your neighbor know what kind of junipers they are? We could do a bit of looking around at natural habits if we knew that.