Desktop.getDesktop().getComponentByName("componentName");
Thus, the properties of any component inside the Desktop can be changed from an external process. For instance, if you want to set the foreground color of the text field named USERNAME to red, use the following code:
((TextField)Desktop.getDesktop().getComponentByName("USERNAME")).setForeground( new java.awt.Color(255,0,0));
You can also get access to the main components WorkingArea and TaskArea by using the corresponding getter methods available in the Desktop class (getWorkingArea() and getTaskArea()).