Update u_e-sogo.md

docs/u_e-sogo.md

@@ -1,10 +1,41 @@
 
 SOGo is used for accessing your mails via a webbrowser, adding and sharing your contacts or calendars. For a more in-depth documentation on SOGo please visit its [own documentation](http://wiki.sogo.nu/).
 
-## Change Theme
-As of December 21 2018 we removed our custom themes due to complains about missing colors in some address book and calendar sections. Some other problems were still existing and would not be fixed in the near future (switching colors on login screen, for example).
+## Change theme
+mailcow builds after 28 January 2021 can change SOGo's theme by editing `data/conf/sogo/custom-theme.js`.
+Please check AngularJS Material [Intro](https://material.angularjs.org/latest/Theming/01_introduction) and [Configuring a theme](https://material.angularjs.org/latest/Theming/03_configuring_a_theme) documentation to get more details on how this works.
+After you updated said file you need to restart SOGo and Memcached containers by executing `docker-compose restart memcached-mailcow sogo-mailcow`.
 
-## Change Logo
+## Reset to SOGo default theme
+Checkout `data/conf/sogo/custom-theme.js` by executing `git fetch ; git checkout origin/master data/conf/sogo/custom-theme.js data/conf/sogo/custom-theme.js`
+Find in `data/conf/sogo/custom-theme.js`:
+```
+// Apply new palettes to the default theme, remap some of the hues
+    $mdThemingProvider.theme('default')
+      .primaryPalette('green-cow', {
+        'default': '400',  // background color of top toolbars
+        'hue-1': '400',
+        'hue-2': '600',    // background color of sidebar toolbar
+        'hue-3': 'A700'
+      })
+      .accentPalette('green', {
+        'default': '600',  // background color of fab buttons
+        'hue-1': '300',    // background color of center list toolbar
+        'hue-2': '300',
+        'hue-3': 'A700'
+      })
+      .backgroundPalette('frost-grey');
+```
+and replace with:
+```
+    $mdThemingProvider.theme('default');
+```
+
+## Change favicon
+mailcow builds after 30 January 2021 can change SOGo's favicon by replacing `data/conf/sogo/custom-favicon.ico`.
+After you replaced said file you need to restart SOGo and Memcached containers by executing `docker-compose restart memcached-mailcow sogo-mailcow`.
+
+## Change logo
 mailcow builds after 21 December 2018 can change SOGo's logo by replacing `data/conf/sogo/sogo-full.svg`.
 After you replaced said file you need to restart SOGo and Memcached containers by executing `docker-compose restart memcached-mailcow sogo-mailcow`.
 
@@ -34,5 +65,5 @@ Restart SOGo: `docker-compose restart sogo-mailcow`
 
 Edit `data/conf/sogo/sogo.conf` and **change** `SOGoPasswordChangeEnabled` to `NO`. Please do not add a new parameter.
 
-Run `docker-compose restart sogo-mailcow memcached-mailcow` to activate the changes.
+Run `docker-compose restart memcached-mailcow sogo-mailcow` to activate the changes.