How can I modify data while parsing it?

I'm new to CKEditor, and currently my task is to add a button that when pressed - will color all the repeated hyperlinks in the Editor.

I was planning to det the data using editor.getData(), parse it, then return back to the editor using
editor.setData().

My problem is that when I'm using parser.parse(), I can't seem to be able to modify the data. I use parser.onTagOpen to identify the links, but when I do, how can I change their attributes?

Any advice is much appreciated!