Ok. *rubs hands like the fly.
First. Normal moden color photography can make color darker and less saturated (less pure) than in real life, BUT Cinderella (and most of Disney's color output) wasn't shot on color film, but in BLACK and WHITE film, in the TECHNICOLOR sequential color separation tri-frame process.
When you shoot IN Technicolor you use black and white film, shooting through three very pure, narrow band color filters,
Red Green and
Blue. So actually except for very extreme ultra pure color wavelengths along the color loccii

(The edges of human color vision

) all colors are recorded without degradation cus it's filtered b/w photography. It's the purest form of making a color record. There will be no degradations, Bounty Hunter. *breathes hard
Now, Disney negatives then were printed in the Technicolor inbibition dye print process (Called Technicolor IB prints or something

) in which the black and white separations are exposed into the purest
Cyan Magenta and
Yellowcolor dyes separatedly and then overlayed one on top of the other to make a color image. This proccess apart from using pure color dyes and they being physically separated also offered great flexibility in manipulation, contrast control, and color masking (a proccess where you can "cheat" any color to look brighter or change hue to the way you want it when combined with others in the printing stage).
Also Technicolor color dyes don't fade (the prints just explode or catch on fire if they were made in Nitrate base

) unlike modern color dyes.
The printing sequence (simplified) is:
Technicolor
RGB b/w negative --> Technicolor
CMY dye assembly IB print
Sooooo in a sense , "When shooting onto film, the colours would have gone darker" doesn't nessesarily happens with Technicolor-shot films, in fact, if you want to, you can make colors be brighter and more saturated than in real life by manipulation (kind of like today when we do it in Photoshop).
With normal "modern" color film (like Eastmancolor, Kodacolor, Fujicolor, Ektachrome, Fujichrome, etc), it's a totally different process than Technicolor: the 3 light sensitive silver b/w layers are on top of each other in one film, the color filters are on top of them, and the three color dyes are on top of each other piggybacked and attached to the b/w silver layers and they interact chemically and optically when exposed and have color crossover and impurities. So the colors get darker and less pure (cus they're mixing with each other). To minimize this, since color negative is not seen directly but used to expose subsequent printing elements, it includes that
orange color mask that you might have seen on them: it's a chemical trick to minimize the impurities of 2 of the color layers. Modern print film of course, since has to be seen directly, can't have the
orange dye mask, so it degrades the color more.
While with Technicolor prints, since the dyes are exposed directly from the pure b/w records and physically separate, don't have these multilayer interaction problems and as i said, even if any errors would occur (cus Technicolor dyes, tho being the purest, are never totally 100.00% pure) between the light passing interactions of the (almost pure) color magenta cyan and yellow dyes when laid on top of each other, they could be corrected and manipulated in the printing stage .
On the other hand, on modern color prints, the modern multilayer films printing sequence is:
negative (
orange) --> interpositive (
orange) --> internegative (
orange) --> print
and there are 4 chances of color deviation accumulating by the time yoiu reach the print.
(The orange masks minimize the accumulation of error but dont eliminate them)
That's one reason i'm always saying that videos are not usualy made from prints since there are several earlier film elements that have better image quality and color than a print.
Now Disney Technicolor films (and shorts) might have been reprinted into modern color stock (Especially since Technicolor stopped making Technicolor prints in the 70's

)
Like this:
Technicolor
RGB b/w negative --> interpositive (
orange) --> internegative (
orange) --> print
And this could be the source (or film elements) that might have been used in various video edition tv broadcasts and film prints you might have seen in the theaters in relatively recent times
For example in the laserdisc era (90's) , when they resored Fantasia
when you went to the theater you saw
Technicolor
RGB b/w negative --> interpositive (
orange) --> internegative (
orange) -->
print
And on the Laserdisc (and the particular R2 PAL dvd variation I have (not the UK R2) made apparently from that restoration) the video master was made from:
Technicolor
RGB b/w negative -->
interpositive (orange)
Same as the Gone With the Wind Laserdisc
Now with "Ultra-Resolution" -like processes and probably for the Disney modern restorations, they're probably scanning directly the
Technicolor RGB b/w negative
onto computer
RGB or digital video master, and that should give the purest results, only limited by the knowledge/technical saavy of the operator, and the RGB primary phosphours of the NTSC/PAL/SMPTE 'C" or HDTV system and your color display. (Since the b/w RGB separations hold the whole color gamut and it's bigger than any modern TV system's gamut)
The versions you might have seen before , if made from modern color film stock, not Tecnicolor prints, would have less purity in colors and probably hue errors and changes of lighteness, than the original Technicolor prints or what's on the negative. Also, consumer TVs, most of them arent very good at reproducing the full color gamut of even of the limited NTSC,SMPTE, PAL etc color spaces
"I think her hair was always meant to be a light brown, and years of wear caused the film to make her hair a darker, reddish color."
Years of film wear dont make changes in color, it's the years of different color systems, changes in film stocks, copying, etc

Film wear makes scratches!
(Time and light exposure can make modern color film color dyes FADE, (become more transparent) but thats a totally different thing than colors "changing". A faded color film looses contrast , or gets an overall color tint (like reddish cus the cyan layer dissapears, or magenta cus both cyan and yellow layers dissapear, which when reversed on the nagative/positive process becomes cianish or greenish respectively, or cyan (like posters left too much time in direct sunlight in video stores

) cus the yellow and magenta layer are bleached by the sun, etc but that's not individual colors getting lighter or darker or changing hue color etc

)
(Also remember that true Technicolor Print's dyes don't fade

)
So hopefully these restorations are being truer to the purer original color the films were supposed to have.
Now come my dethi rant worry
"I trust Disney with these restorations. They always look back at the original animation cels to determine their proper colors. If things look differently from older masterings, it's because you're seeing what the animation cels would look like with no film or camera lens in the way"
Well that's not exactly what they should be doiing
That gives you the original colors of the original animation cels. But DETHI RANT HERE : THAT might not be the way the film originally looked or was intended to look like.

Remember the section about where with Technicolor you could manipulate and enhance or mute the colors at will and change hues etc? Well, what they should be referencing to and oogling at the same time might be a Technicolor reference print
I mean the Technicolor printing process was as much part of the intended look as the camera photography. It's like a Master Photographer printing a negative onto a custom print
The print might look a lot different than the original subject looked like or what the negative recorded
I've seen "restorations" that dont look as bright and colorful as the original look because of this . Or where they totally changed the look. Even some highly praised ones
(Think's of one that even changed the intensity of the scene so much by changing it from bathed in warm orange red color into neutral natural lighting color

that it changed the intention of the original scene, which was kinda like the ending of the movie
Hopefully in the best of cases Disney and others know what they're doing and will get things right or nearfully right
UDmembers beware
