How to Change the Color of the Combobox popup?

[DominikBabic06]

I recently started using material Design in my wpf application and im struggeling with the combobox as it doesnt use the colors i have set as my custom color theme.
As you can see the in the Picture my combobox has this dark grey inside of the popup but my main theme is that blue im using outside.
The style was automatically set when i was creating the combobox and this is the colortheme i set in my app.xaml.

<materialDesign:CustomColorTheme BaseTheme="Dark" PrimaryColor="#B0BEC5" SecondaryColor="#90A4AE" />