Personally didn't notice any difference.
On my recent trip to NYC, went into Barney's. One of my stops was at the Serge Lutens department.
I cannot say this for all the fragrances, but the one I noticed was Chergui. The liquid in the Bell Jar was 10-15% darker in color than the Export bottle. I tested each on different wrists. Although the smell was almost identical, I felt the juice in the Bell Jar was denser, and lasted longer.
Do not know if my mind was playing tricks on me, because the juice was definitively darker in the Bell Jar, or if indeed there is a difference between the two.
Anyone who has tested both together, would like to hear your thoughts.
Personally didn't notice any difference.
Some SL did go through reformulations, and several BNers have mentioned that the current Chergui export is weaker than it used to be. So it is possible. But I have not smelled myself.
cacio
I would guess your perceived coloration difference are more likely related to optics rather than different formulations.