You many have a template that uses a dark background and need to change the colour of your editing area to match. This can be done in the editor’s plug-in parameters…
 

 

Changing the background colour

To do this please login to the backend of your site and visit ‘Extensions’ (which is in the top navigation menu) and navigate down to the ‘Plug-in Manager’ menu item. In the Plug-in Manager use the ‘Filter’ to locate the 'JoomlaCK' plug-in and then click on the 'Plugin Name' to edit and open up into a screen-called ‘Plugin: [Edit]’. On the right hand-side you will notice a list of parameters. Navigate down to 'Advanced Parameters' and define the colour property in hex code. 

To apply the change click on - Save.