Possible Treemap Limitation in Excel?

• I've been having a lot of trouble formatting excel treemaps.  There seems to be a lack of control in colour  formatting.   In a 2 category tree map, There is a design option that gives you grey banners for category 1.   Unfortunately, when you try and change the series colours, it changes the colours for the the series, as well as for the banner.   And I cannot find an option to change the colour of the banner at all.  Is this just something that's just not available right now?  Anybody know?

Thanks!

Jason