The menu in the Compose window has an option to set the message priority. IIRC it's under Options.

Thank you! Although the recipient now sees the "Priority" I was hoping it would display the message header in red or in some additional manor that would bring attention to the message. But this can work. Thanks again for responding.

Colouring or highlighting is a function of your correspondent's email client.

The address and subject lines have to be robust and certain to be displayed regardless of variations in encoding, character sets and so on, so are deliberately kept simple and therefore they don't support fancy formatting commands. Even Unicode emojis (which ought to work) tend to be a bit hit and miss.

Thank u for taking the time to respond.