When you have multiple background colors and text colors in your WBS, these colors carry all the way across the Gantt chart so the summary tasks have the same formatting. This can make the resulting output look like someone melted a box of crayons across your schedule. It would be nice to only have this formatting apply only to the columnar text data; i.e. provide an option to turn it off for the gantt chart area to provide a cleaner look.
How about an option in the WBS Layout dialog for "Do not color Gantt Chart" (or "Color Task list only")?
With the result like this: