There are no exposed properties which control the HeaderBackground or the ToggleButtonStyle. However you could extract the default style of the RadDiagramContainerShape and apply your modification. If you make that style implicit it will be applied across all your RadDiagramContainerShape's. You can find more information on how to extract the Template/Style of our controls in this article
I have modified the default style and added Background to the Grid holding the header and the button. However you could change it based on your needs. As for the Style of the RadToggleButton you can apply it directly to the button in the template.
I have attached a sample project with the custom style for your convenience. Please let us know if you need further assistance.