How to reset the terminal properties and preferences?

Try gconftool --recursive-unset /apps/gnome-terminal

Ubuntu 16.04

This simple command works in Ubuntu 16.04.

dconf reset -f /org/gnome/terminal/legacy/profiles:/

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Reset only the default profile

However, if you want to reset only the default profile, which uses UUID b1dcc9dd-5262-4d8d-a863-c897e6d979b9 by default, you can use

dconf reset -f /org/gnome/terminal/legacy/profiles:/:b1dcc9dd-5262-4d8d-a863-c897e6d979b9/

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^{Note: This method should work in Ubuntu 15.04, 15.10 and may work in 14.04 too! But I haven't tested on those versions}

In terminal click on the 'Edit' menu then 'Profile Preferences'. It will pop up the 'Editing Profile' Window. to reset the color make sure that you have selected the check box named 'Use colors from system theme' in the 'Colors' tab.