EDIT: Never mind, figured it all out.
For those who’s text won’t render as html, remember to use textfield.htmlText.
For stylesheets, use:
var style:StyleSheet = new StyleSheet();
var styleObj:Object = new Object();
styleObj.display = "inline";
styleObj.color = "#2DAAFD";
style.setStyle("highlight", styleObj);
this.theTextField.styleSheet = style;
//in a text field, use <highlight>the highlighted text</highlight> to use the style.