Dear Nikolai,

Many thanks for your message and the links you provided.

This was really helpful and after several attempts, I finally succeed with the extend method.

I have another question :

How can I replace the text logo by an image logo ?

Thanks again.

Have a nice day.

Thierry 

The links below are for previous Elgg versions but should work for the current release as well:

https://elgg.org/discussion/view/2804746/logo-in-default-theme-in-all-stable-elgg-version

https://elgg.org/discussion/view/2849336/how-to-change-the-logo-from-text-to-image

I forgot to mention that the easiest way to extend engine/theme.php is to use a hook in elgg_plugin.php instead of class:

'theme' => [
     'body-background-color' => '#000',
     'anchor-color' => '#000000',
],