GanttDiva is very flexible and allows you to customize the colours of your Gantt chart as well as setting default colours the title area, background as well as default colours and patterns for all the shapes that are drawn by the program.
GanttDiva also allows you customize task colours based on the Project Name, Resource or Task owner assigned.
You can even change the size and transparency of the shapes drawn by on the Gantt Chart. This is because all tasks and milestones are drawn as shapes, rather than just as coloured in cells. This also means that tasks are always drawn correctly to match the duration and the Gantt Chart timescale.
The result is a Gantt chart that is completely customized to meet your needs.