Would this detective work be a fairly easy task for a PhotoShop adept?

I don’t think it would be that difficult if you can easily discern the difference in ink colors. A good photoshop person could dial in on the exact color and eliminate that color.

But it doesn’t mean they can resurrect the original. Where the new color overlays the old color does not necessarily appear as layered in a digital image. Those are specific pixels, and when you take one color out of the pixel, it does not necessarily replace it with the original color.

This is all conjecture, I am no expert at photoshop or digital images.

What you need is an expert at manuscripts. Original texts are still being found on medieval vellum that was reused.

I would use negative feature to turn picture into a negative and then zoom in very close to see the different colored lines lines.( do not turn image into black and white for this to show the differences).
To make it even clearer…edit out the lines covering the original words..this takes hours of painstaking patience to wipe out carefully.
Other photo software has different and advanced methods of obtaining.

Located this online as a way to remove successfully by hand.

https://lifehacks.stackexchange.com/questions/10139/remove-ink-thats-scribbled-on-top-of-printed-text

Infrared is used on artworks to uncover the underlying drawings and earlier versions. i don’t know how accesible that is to the layperson but it might be useful.

A bit of foreword, I’m not a document expert, but I’m pretty handy with Photoshop. I’m filling in more details than usual just in case this is a thought experiment for a story, or something along those lines.

I think the biggest advantages digital editing could give you are
– enhancing the difference in colors so you can make out more details
– magnify the whole thing to a point where something additional is clear. (this also depends on a high DPI scan, 600+ if you need numbers)

You may in that process find that there’s actually a difference in color where the inks cross as well, but I’d be guessing without looking at it. Backlighting might help here as well.

You can remove colors, as mentioned above, pretty easily in Photoshop, but again that doesn’t make a layer below in the physical thing accessible, it’s still just each pixel’s color stored as an image. Just like I can remove a building from a photo, but it doesn’t mean I can tell if someone is standing behind it, or inside it.

The other somewhat related technique is that using script samples, we’re getting to the point where machine learning could infer what letters are used in the original script from the small parts you can see (ascenders and descenders for example), but that’s a bit more setup and expertise.

CSI style “enhance!” has done us all a disservice.

It’s possible. It depends on the colors and how they physically are layered.

In days of yore, before Photoshop, I ran a darkroom where we made museum-quality prints from client’s old photos. Someone brought in a beloved black and white photo which her kid had defaced with red crayon. I copied it with a red filter, and the crayon was absolutely invisible in the reproduction. It was one of my proudest moments in the job.

@Call_Me_Jay beat me to it. Color match the new ink. Fill a new layer. Adjust transparency level.

I have to also admit that I learned this trick from a super neat children’s book

It was the inspiration for one of my favourite art lessons. I have the kids draw pictures in light blue markers. Then have them scribble all over in red marker. Then we make secret decoders using red plastic film.

I am very interested in palimpsests, though I’m not sure this case is actually such a manuscript. I hope you’re able to get resolution.