Ok I see. The slice controller area of the slice views. Have you registered a custom layout in that image there (as in customize view layout)? That’s how a custom layout can be created which allows you to specify different colors for the slice viewers. I’m not aware of a a specific layout view that looks like that in the latest versions of Slicer.
As it relates to python autocomplete you can see the state of things from this older thread. Note that I really haven’t tried it any further. As it relates to figuring what methods are supported by various objects I often use the python interactor in slicer and just use tab completion to look into the available methods. So like volume_node.[PRESS TAB].
Some further python debugging content can be found linked from https://slicer.readthedocs.io/en/latest/developer_guide/build_instructions/windows.html?highlight=python%20interactor#debugging-python-scripts.