I'm not aware of a native FM SQL function returning text as styled text. We also can't use ExecuteSQL ? parameters to do this, because they evaluate once at the start of a query.
I think you'd need to use an unstored calc field to forcibly cast rich text into CSS upstream. It's simple and fast, but of course adds clutter and non-semantic fields. Here's how to do it:
1) Given a text field "styled_text", create an unstored text calc field defined as "getAsCSS ( styled_text)".
2) In your SQL, simply select this unstored field. Output looks like this: