When it is enabled, all boxes get a bright teal border,
padding (from widgets like Padding) is shown in faded
blue with a darker blue box around the child, alignment
(from widgets like Center and Align) is shown with
yellow arrows, and spacers (from widgets like
Container when they have no child) are shown in gray.

The debugPaintBaselinesEnabled flag
does something similar but for objects with baselines.
The alphabetic baseline is shown in bright green and the
ideographic baseline in orange.

The debugPaintPointersEnabled flag turns on a
special mode whereby any objects that are being tapped
get highlighted in teal. This can help you determine
whether an object is somehow failing to correctly hit
test (which might happen if, for instance, it is actually
outside the bounds of its parent and thus not
being considered for hit testing in the first place).