Selected background of email doesn't "stick"

[ineuw]

It seems that setting the background of emails in Options \ Composition, affect only the incoming mail. I see the selected color flash by when I create a new mail, so I don't know for sure. Could someone please enlighten me how to use the same color without a template?

[DanRaisch]

Have you checked any of the messages in your Sent folder that went out after making that change to the background color?
Are you composing messages in HTML format or plain text?

[ineuw]

Always using HTML, and just checked the Sent messages a day after selecting a color background, and none of the mail sent since have colored backgrounds. However,
the color always flashes by as I open a sent document or, when clicking to Write a new message. Would this have anything with the recipient's address book settings? But then, it's white before I select a recipient.

[ineuw]

It began working suddenly. I don't know what triggered it after 24 hours, but it works now and if it stops working, so be it. Thunderbird works in mysterious ways.
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Added:
Curiosity got me to test Thunderbird on Windows, Xubuntu 14.04 and Mac OS X10.75.

Macbook: There is no Format on the menu bar. The option is available only through Preferences\Composition and the change is effected instantly.
Xubuntu: There is Format on the menu bar. The option is listed in Preferences\Composition and on the Menu bar under Format\Bacground colors, the change is effected instantly, but is unknown which of the two is effective.
Windows: There is no Format on the menu bar. The option is available only through Preferences\Composition and the change was effected after using CCleaner, so one must assume that this setting is registry related.