Apple Motion 4 - Manual (Page 334)

The order of two objects affected by the Linear Dodge blend mode does not matter.
Overlay
Whites and blacks in the foreground image become translucent and interact with the
color values of the background image causing intensified contrast. Whites and blacks in
the background image, on the other hand, replace the foreground image.
Overlapping midrange values are mixed together differently depending on the brightness
of the background color values. Lighter background midrange values are mixed by
screening. Darker background midrange values, on the other hand, are mixed together
by multiplying.
The visible result is that darker color values in the background image intensify the
foreground image, while lighter color values in the background image wash out
overlapping areas in the foreground image.
The order of two objects affected by the Overlay blend mode is important.
Boxes object on top Monkey object on top
334 Chapter 7 Basic Compositing