//create title default sheet
var defStyle:StyleSheet=new StyleSheet();
var styleObj:Object=new Object();
styleObj.color="#"+"FF0000";
defStyle.setStyle("p",styleObj);

//add sheet to text
txtField.styleSheet=defStyle;

//add the text
txtField.htmlText="text here";

//create title default sheet
var titleStyle:StyleSheet=new StyleSheet();
var titleObj:Object=new Object();
titleObj.color="#"+mainXML.settings.titleDefaultColor;
titleStyle.setStyle("p",titleObj);

//add sheet to text
mcTitle.txtField.styleSheet=titleStyle;

//add the text
mcTitle.txtField.htmlText="text here";

Default stylesheet for text field

ActionScript 3