I suspect that external styles surrounding the edit area iframe are not being inherited into that frame.
(pseudo html)
#mainpane h3 { color: red };
<link href="~\style.css">
<h3>Heading</h3> // Appears in red as expected
<CE:Editor Text="<h3>Heading</h3>" EditorWysiwygModeCss="~\style.css"></CE:Editor> // h3 text appears in default black
Placing the surrounding <div> into Editor.Text (<div ID="mainPane"><h3>Heading</h3></div>) produces the correct result.
Is there any way of making the iframe aware of the #mainpane region (progmatically) without changing the Editor.Text?
TIA