Untested:

td ({-style=>"foreground:red"}, escapeHTML("This is a required field")
+);
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The HTML shortcuts take an optional first argument, a hashref with the elements attributes.

Or you could do:

td (span ({-class=>"required_field"}, escapeHTML("This is a required f
+ield")));
[download]

And use a style sheet to colour spans of class required_field red. Or you could give the table cell a class (or id) attribute.