I just did one of these last week! Print an emblem off the computer the size that you want. Cut it out with an exacto knife and use that as a template. Cut the main piece with gray gumpaste and brush it with silver luster dust right away before it dries. Then cut the inside pieces with the navy blue and just adhere it to the silver with some water or edible glue.
It was actually super easy and took maybe an hour start to finish. :)