So your friend has milk and honey every evening. Then she goes to her bedroom and opens her emails.

How about sending her messages fit for the hour: not in black and white but maybe gray and black?

In Mac OS X Mail, changing an email's background color is easy—but you have to know where to look.

Change a Message's Text Background Color in Mac OS X Mail

To set the background color of a message you are composing in Mac OS X Mail:

• Select Format | Show Fonts from the menu (or press Command-T).
• Click the Document Color button (it shows a document icon).
• Choose the desired color from the desired color picker.

Note that you can only change the entire message's background color and not, say, highlight selected text with a different color.

(Updated April 2015, tested with OS X Mail 8)