A frequent question that comes up with the new Telerik provider is "How do I change the background color of the editor" and  "How do I get my styles to show up in the CSS dropdown". The issue is that the editor is going to import skin.css by default, and if you have a background color or image set on the body tag, it will use that for the editor background. Also, it will look for any css classes and add them to the css style dropdown of the editor. We don't want that because it can get very messy. Luckily, we can kill two birds with one stone.

 

1. In the portal root folder, create a css file called editor.css

2. Add body {background-color:#fff; background-image:none;} to the css file

3. Add custom styles that you want to appear in the drop down. These styles must exist in skin.css as well.

4. Save, rejoice.

 

You should ensure that editor.css is enabled in the Provider settings (Host > HTML Editor Provider), but it should be default. In the help icon it states

The css file to be used by the editor in wysiwyg mode. This file must reside either in the skin directory or in the portal directory. The path set here is relative to its parent (e.g. /editor.css is a file in the root of your skin) 

But I have had better luck putting the file in the portal root rather than the skin root.