How to change column header's background color when using WPF datagrid? Need to modify xaml directly?
Use a style with a setter targeted at DataGridColumnHeader:
<DataGrid>
<DataGrid.Resources>
<Style BasedOn="{StaticResource {x:Type DataGridColumnHeader}}" TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="Background" Value="Blue" />
</Style>
</DataGrid.Resources>
</DataGrid>