That is a very subtile difference, but noticeable. I do not think that using white props will reveal the issue here because if you look closely at the forehead skin color, its final color is affected by having light passing twice through a transmap (going in, and then back out).

Just a suggestion, to reveal (duplicate) the issue, you'll likely need to paste a color strip as a texture on the box primitive. The forehead's color is more red/blue now, as if a little bit of green has been subtracted.

Good luck with this!  : )

 Don't sweat the petty things, and don't pet the sweaty things!  ; )