Hi toofan,
You can't change the information *directly* in the Relationship Diagram view
in the bottom pane, but you can modify task link types (FS, SS etc.) in the
Task Form View. When you initially split from the Gantt Chart view, the
Task Form is the view in the bottom pane. Click in the bottom pane and
choose Format > Details, and you can display Predecessors and Successors in
the task form.
As far as changing the color of task cells, I'm afraid that is impossible.
Unlike Excel, there is no "fill" color to change the background of a task
cell. You can change text color, size, etc through Format > Font.
I hope this helps. Let us know how you get along.
Julie