Good morning Janne,
You don't need to use a plugin, you can actually do it in the Editors Css stylesheet itself. Take a look at this article.
Hope this helps
use the above links, hope helpful to you.
I'm trying to customize the class menu available in TinyMCE table plugin. I tried using empty .cs class with attribute TinyMCEPluginNonVisual:
But without success. Does anyone have working solution to this? I've successfully used class attribute similar the one above in EPiServer 6 projects. But now I did not get any effect with this solution, menu is populated with some epi prefixed class + our custom classes from editorsstyles.css created for the "style" menu in editor toolbar.