How to input internal CSS to content items with CKeditor
If you are using Filter HTML go to: 

/admin/config/content/formats/filtered_html

add the &lt;style&gt; tag to the limit allowed html tags



If the above does not do it, depending on which one you are using (filter or full html) You need to go to 

/admin/config/content/ckeditor/edit/Advanced (for Filter HTML)

/admin/config/content/ckeditor/edit/Full (for Full HTML)

Then under Advanced Content Filter, select disabled.