In an ealier post called Valid XHTML - the blogger navigation bar i looked at the navbar. The navbar is called as a seperate webpage with certain parameters one of which is navbarType that per default has the value BLUE with the new XML templates (I didn't use blogger before so I have no real knowledge of how it used to be. I seems obvious that this is a way to style the navbar, but it's not obvious what values are allowed and I haven't found a setting for it in the Customize section.
A search on Google for NavbarType blogger didn't give any obvious hits on the blogger help or discussion forums, but i did see some of the valid color themes like ex.:
but not ex.: