Deoldify Vapoursynth filter

[Selur]

side note: you should make sure to crop away all black bars before applying retinex

No, there is no way to reverse the effect of applying Retinex.
You could apply it after the colorization, by adjusting the FilterOrder under 'Filtering->Vapoursynth->Filter Order/Queue'.
(read: [INFO] About Vapoursynth Filter Order/Queue)

With a custom script one could:
a. copy the clip before applying Retinex
a. apply Retinex on the clip
b. apply DeOldify on the clip
c. take the chroma from the filtered clip to the previously copied clip

!Untested! (just an idea, some small adjustements might be needed)
In Hybrid this could probably be done by:
1. creating a custom section before applying Retinex

global before_retinex = clip

2. creating a custom section after applying DeOldify

chroma = core.std.ShufflePlanes(clip, planes=[1, 2], colorfamily=vs.YUV)
clip = core.std.ShufflePlanes(clips=[before_retinex, chroma], planes=[0, 1, 2], colorfamily=vs.YUV)

Cu Selur

[zspeciman]

Thank you Selur, the cropping out the black border works really well.  There was very little cropping but the difference is significant.
The reason I wanted to reverse Retinex is these blocks that are formed. See attached pics.  Any suggestions how to reduce that?  I thought restoring the video to its original darkness would do the trick.   Perhaps there is a dithering method to apply here, if such a tool exist.

[Selur]

You could apply strong blocking with a LimitMask before Retinex, that should at least reduce the blocking.