3D anaglyph (fashion) retouch problem.

[quim]

Hello,

At the moment I'm working on a 3D anaglyph fashion story, but ran into a strange problem.

Both images have a 100% desaturated background, but when i disable the R channel in the top image for the 3D effect, the background gets a graduation that
has a higher R value as the G,B on the left, moving to neutral, and gets a lower R value as G,B on the right..

I don't understand how this happens, and if there is a solution for it?

I've attached a jpg of the top part of the background.
the small block on the left is the Left image (not overlapped by the right image yet)which is neutral.
i've marked the left side of the Right image with a white line, as you can see
this starts directly with a Red cast moving to neutral and then to Greenish cast

extra info
---
My workflow is:
left camera image is background image
right camera image is on top
In each image I 100% desaturate the background
In top image disable the R channel in Layer Style.
then i move the right image so the eyes will overlap, as this will give a "clean" face without 3d glasses as well.

all images are shot in a white limbo, which is a bit darker due to light fall-off to background.

Any other tips to retouching a 3d person are welcome as well.
Small transformations and retouches i do for each image separately.
bigger transformations and D&B skin retouch i'll do on top when the 2 images are merged.

thanks