Login as Site Admin
Go to Store Admin page
Go to Ship Orders
Select one of the orders
Click on Send Ship Email button.
A confirmation message is displayed like below:

Ship Confirmation Email Sent Successfully

Styles of this message and some of other confirmation messages are coming directly from ASCX file, instead of module styles. This means we need to inspect all of span ids like this and create/modify css with manual efforts.

Please consider implementing CSS support for confirmation messages.

Warm regards.