Match the color of an IRL painting to a scanned version.

[foggy lark]

Generally you will have to use curves (with the 3 or 4 channels to be tweaked individually, and possibly having multiple curves (or other types of layers depending on the initial aim) . You'll be using the tools of standard colour correction.

I would be a deep subject to go into if you're new to this, and more approacble if you got a little experience using photoshop.

If you are not in a hurry, and can scan the artwork again, get yourself one of these
https://www.skearsphoto.com/photo-editing/perfect-pixs-digital-mini-3-tone-cards.html
that you will scan alongside the artwork. You will then have a target that you can use to determine what is real black, real white, and crucially a middle grey.

THere are two ways to colour correct in Photoshop:
Using the curves, Hue saturation, colour balance etc... with masks, and using what is called the Camera Raw Filter.
(certain scanners also have an inbuilt colour correction tool, but I wouldn't use it)

Because you need hard data for this kind of stuff, you will have to use the colour sampler tool, alongside the info panel, unfortunately, you don't really have a print/digital file that you know is of the right colours to help you. Just your eyes (and your eyes aren't accurate, surrounding colours and luminosity, like for example the yellow nature of bright summer sun, or the colour of the lightbulbs you're using will affect your vision), so you will have to rely on an external, known target (the piece of cardboard with printed tones above)
And you will know if that black in the painting is really black (they generally aren't, real black in acrylics or oil is quite difficult to attain, and to an axtend, same with white + the medium, even paper, is rarely neutral white)

Of course, it depends how far into the rabbit hole you want to go.

A couple tutorials
https://www.youtube.com/watch?v=Eod-MgCcVxI

https://www.youtube.com/watch?v=heUomkB7vuE

https://helpx.adobe.com/photoshop/using/adjusting-color-tone-cs6.html

But any tutorial on colour correction (you'll find most on portraits) will do.
The only thing is that you have a real life reference, but you need to keep in mind that the colours as you see them in that real life artwork are heavily dependent on your environment, and that your scanned version isn't dependent on them.

[primal fractal]

The grey card is exactly what I wanted to suggest.
It seems that some of the tones in the glass could be neutral, and the eyedropper could be used on it…

Is there a way to disable auto corrections in the scanner driver?

[foggy lark]

Yes, I forgot to list it: If you know for a fact that an area in the painting is neutral then it's easier to set up the primary colour correction. (all 3 channels Red, Blue and green will have to show with the same number like 125/125/125)