Change Modal Header Color

I am using a bootbox confirm and wanted to change the color of the modal it opens.

You can change the button colors when setting up the action and I changed the body and footer by changing the “modal content bg” property in theme manager, but I can’t find anything for the header.

This is what it looks like when the modal pops up from an action.

Am I just blind or does the option not exist? And if it doesn’t exist how else can I style the header?