Illustrator Scripting :: Iterate Through Selected Characters

Code snippet to show me how to iterate through the selected text (not the frame!, not the words, only the selected chars) and make any change on the characterAttributes (size, color, etc.)?
 
In the property "app.activeDocument.selection" usually the selected objects are stored as an array. Now when I select characters in a textframe (or TextPath, whatever) there is a [Textrange] in it. I already tried some combinations like this snippet underneath but I still get errors, that selectedChars[i] is undefined.I'm on Illustrator CS4, Mac OS X, Javascript
 
var selectedChars = app.activeDocument.selection.characters;
for (i = 0; i < selectedChars.length; i++ ){                           
selectedChars[i].characterAttributes.fillColor = myNewCMYKColor;