The problem here goes beyond a color shift. There just isn't any useful color information in left image

The original color film had cyan, magenta, and yellow dyes. It appears that the cyan and yellow have almost entirely faded, leaving just the magenta — the pink hue.

I'm guessing that the first sample scan has had green adjusted to be more gray as an attempt to neutralize the shift (making it look very much like an intentional effect.) But maybe it's just like that.

If you crank the saturation up like crazy you can see:

But the point is: there's no useful, real color information in this file. Crucially, note that in the reference, the truck exterior, truck interior, shrub behind, and building to the right all have different hues. That has been lost.

With lesser amounts of fading, one can correct easily with the Color Balance tool in Gimp (or other software like Photoshop). But here, there's not not enough distinct information for that to work. It just ends up re-casting the mostly-gray overall image.

I don't think there are any fixes to this image file, really. That leaves these options:

• Recolor by hand. Since you have a reference, and it's mostly big blocks of mostly-solid colors, this wouldn't really be that hard.
• Embracing a false color look as in the alternate answer here.
• Possibly, you could get a new scan using color-correction abilities built into the scanning software. Even if that's not perfect, it may give you a starting point from which you can get more real results.
• Or: remove the photograph from the frame and glass and scan that. That's clearly also faded, but at least there's something to work with.