How to change color of header text?

[Imadlekal]

<dragablz:TabablzControl FixedHeaderCount="3" >
            <TabItem  Header="HELLO">
                <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">Hello World</TextBlock>
            </TabItem>
            <TabItem Header="MATERIAL">
                <StackPanel>

                    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">Material Design</TextBlock>
                    <Button
                        Style="{StaticResource MaterialDesignRaisedDarkButton}"
                        Width="100"
                        ToolTip="Resource name: MaterialDesignRaisedLightDarkButton">
                        _DARK
                    </Button>
                </StackPanel>
    </TabItem>
            <TabItem Header="DESIGN">
                <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">Looks Quite Nice</TextBlock>
            </TabItem>
        </dragablz:TabablzControl>

I tried using the Foreground property on "TabItem" (for MATERIAL for example) but that didn't do anything. In fact, it changes the color of the TextBlock inside that tab.

I tried to use Live visual tree to know where the color is coming from but I couldn't, same thing applies for the color under the Tab name. (Selection color).