Ribbon Background

Changing the background of the Ribbon can’t be done by simply changing the Background property. You have to, at least, overwrite the following resources to change the background of the Ribbon:

<Fluent:RibbonWindow.Resources>
    <SolidColorBrush x:Key="Fluent.Ribbon.Brushes.RibbonTabControl.Background">LightBlue</SolidColorBrush>
    <SolidColorBrush x:Key="Fluent.Ribbon.Brushes.RibbonTabControl.TabsGrid.Background">LightBlue</SolidColorBrush>
    <SolidColorBrush x:Key="Fluent.Ribbon.Brushes.RibbonTabControl.Content.Background">LightBlue</SolidColorBrush>
    <SolidColorBrush x:Key="Fluent.Ribbon.Brushes.RibbonWindow.TitleBackground">LightBlue</SolidColorBrush>
</Fluent:RibbonWindow.Resources>