Jim, in trying to understand the medieval taste for coloring, you might find the following post on painted period pieces of arts and crafts helpful:
http://www.vikingsword.com/vb/showthread.php?t=7076
Just scroll down to where I attached the 15th century closets.
Of course you are right to mention a very similar style of decoration on 18th century blades but the painting on this stock is certainly of mid-16th century date. I realize that dating criteria are hard to define. Let me give you an example: When an illiterate person is confronted with a book for the first time, all he can say is "What are these strange marks? How can anobody see a meaning or message in them?" Of course, it takes along and intense process of studying to be able and actually put single letters together to words and sentences - and finally grasp their meaning.
Highly specialized detailed knowledge is very hard to share in being esoteric. All I can do is hope that this does not sound arrogant. I wish I knew how to do that any better.
Nevertheless, try and enjoy.
Matchlock/Michael