Colorblind users will have trouble with your application.

>I tend not to use explicit Edit mode. If a user want to edit some data he (or she) clicks (or tabs right to it) the data and changes it. All the changed data is coloring red just to let user see wich data has been changed. If the user want to undo the data, just click the undo button and the data is coloring blue again.(In my program editable data is colored blue, changed data is colored red, non-editable data is colored black)