Please check the Editor.EditorBodyStyle and EditorWysiwygModeCss property. 

Editor.EditorWysiwygModeCss Property
Specifies the location of the style sheet that will be used by the editable area. Multiple Style Sheets are supported. Example EditorWysiwygModeCss="example.css,~/portal.css,/default.css"  

Editor.EditorBodyStyle Property

The style to be applied to the Editor body.   

Cute Editor uses default font of the current page.  The default font of web page is Times new roman. If you want to change the default font from Times new roman to Verdana, you can add the following code into the style sheet file: