I love the look of cookies with outlines done with one color of sanding sugar and a fill in another, but how on earth do you get it so detailed?

Just a guess, but looks like the blue areas were piped on with RI (or the like) and then coated in the blue sanding sugar. Shake off excess. That was allowed to dry then the yellow areas were filled and coated with sugar.

I have done this before... its exactly what Bskinne said, the blue then the yellow

I'll see if I can't find the site where the decorator discussed the technique. I recall the use of small brush for cleaning the cookie up from stray sugar....I think bskinne's thought on this one may be right. The decorator mention icing the cookie, allowing it to dry then going back and applying the sugar...but that was also where the sugar was use as accent...like at the top rounded areas of an apple or one edge of a leaf.

http://cakecentral.com/cake-decorating-ftopic-614851-0.html

Thanks everyone! Great ideas and that link helped a lot too!