How to add global background color style?

Im trying to use an implicit global style to set the BackgroundColor property of ContentPage like this:

<Style TargetType="ContentPage">
        <Setter Property="BackgroundColor" Value="#ff0000" />
</Style>

This doesn't work. My other implicit style on a Button works but I can't seem to figure out how to globally set style for background.

Maybe Im doing it wrong? Is there a better way to style the overall app look? Make some sort of base page?

Thanks,
Jason