Your link is broken
However, if the problem is because one colour being on top of another, have a look at the image below. They are the same chart: Sales/Profit by Customer and Order Priority is one the colour shelf. To make one mark appear on top of another, simply change the sort order. The easiest way is to drag the items around in the legend. The one at the top of the legend will be uppermost in the viz. Hope this helps.
order of marks.twbx.zip 134.3 KB
You're absolutely right as far as this example goes, but as I discovered (and Joe explained) the Z-Order of marks isn't as simple as this, I wish it were! Here's what he posted in another thread:
Here's a link to that thread: http://community.tableau.com/thread/116655
And if the forum rules allowed, I would post the link to the Idea I posted regarding this issue. Instead you can find it by searching 'Z-Order Mark Shelf'.
PS: Glad you liked the photo I posted in VizTalk. I thought is was rather compelling too. Have a good weekend.