Gantt Charts: How to review Group Header Font and Color

I have created a project Gantt Chart that will be visible in Stakeholder dashboards by project.   The Gantt is grouped by Phases.  Groupings are working well including summary roll up Gantt bars representing the tasks under each phase grouping.   My problem is that the Group row is a smaller font than the rest of the Gantt chart and the Group rollup Gantt bar is an unappealing gray in color.  

How do I control the font size and Gantt bar color of the roll up groups?

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Annetta Coleman
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