I painted problematic marginal area of shape B red.Those red areas are the place where original colors are changed.
it would be helpful to show us the problem at magnified resolution and not paint over it. show before and after.
as for alpha add, here's the resource file where you could read about what alpha add does: Use blending modes and layer styles in After Effects
Alpha add changes the math used to blend transparent pixels. It is often used to fix the problems you are encountering. You can also use alpha add when you face opacity to create a dissolve. This will give you a more of a traditional film quality dissolve. The look will be completely different.
The Alpha Add blend mode only changes the aliased edge behavior in the alpha channel so there is no change in any of the other pixels in the image.
The original problem may be caused by the way you created the transparency in the first place. A complete workflow description with every step detailed may point us to offering a solution or at least a better explanation.
Thank you for your answers. Then those images will be helpful, put those original images into After Effects and simply place them in a composition like I did in my first post. Check the line color of shape B, there will be 2 colors, R0 G0 B0 and R1 G1 B0.
I always edit aliased images, so this color change of fringe area is a problem to my workflow.
I made those image using Photoshop, and B shape line is completely black, color is R0 G0 B0. This only happens in After Effects. When I put those images in Photoshop,B shape line color does not change when overlapped.
I'm not seeing any problems with the edges in AE other than pretty bad aliasing in the black stroke. Here is the image at 100% as a screen capture from a MacBook Pro R 15":
This is with a magnification factor of 1600%
There is no difference when the blend mode is changed to alpha add:
This makes me wonder what else is going on and what version of AE you are running.
You rotated them? Shapes has anti-aliasing. Just place them in composition and see the line color of shape B.
There should be 2 colors and it is the problem. I need to have only 1 color to add effect.
Did you ever solve this issue? Please let us know.