Checkbox content color can't be set in UWP

I'm trying to change the color of a checkbox content. I want the color t change, if the box is checked, but I cannot even change it in the XAML.

<CheckBox x:Name="Checkbox" Foreground="White" Content="I agree" HorizontalAlignment="Left" Margin="50,480,0,0" VerticalAlignment="Top" Height="46" Width="938" FontFamily="Arial" Checked="Checkbox_Checked" Background="#FF009FE3" />

But the content color keeps showing in black. Where is my mistake? Sounds like a simple thing, but I couldn't find any solution out there. I'm new to UWP, what doesn't make it easier as well.