I have tried everything and it seems that the QxTextArea does not honor setColor(). The font is always black. A QxText sets the font color fine, but not QxTextArea. Try this:
a = new QxTextArea("just some text");
a.setColor('red');
this.add(a);
// the font is black
b = new QxText(just more text");
b.setColor('red');
this.add(b);
// the font color is red.
Jim