I'm using windows ToastNotificationManager, right now I create the toast UI like
XmlDocument toastXml = ToastNotificationManager.GetTemplateContent(ToastTemplateType.ToastImageAndText04)
is there a way I can change the background to white or any color also for the text element, can I change the font style, color or size can I even use my own XmlDocuments,I tried but I get system error
You cannot change the background color of toasts. If you're writing a UWP app, you can do more flexible things with your toast, see the toast content documentation to learn more.
The adaptive content section in that article illustrates how you can do some more advanced text formatting (with a few different text sizes).