Lighing, grading, figurine, makeup and sets design... There is a lot of differences from a B&W and technicolor production
But all that can be done is to gradding the B&W image to became more adequate to get colors. IF you see colorized footage of constrasting WW1 or WW2 images, you will see that it do not look good.
Even if you have a prime B&W footage, shoot with B&W film from a real location, natural, with no filter, the colorization would not look perfect, but I must say that can ook very good if well done with modern technology.
Despite technologic advances some nuances are not added with the modern colorization. Many due cost.
In theory it's possible to develop a perfect colorization, but it would require much more work, complete 3D estimation of every piece and character, and tracking of patterns and textures.
There are modern colorized films that are great, like It's a Wonderful Life, and many people can say it look perfect. But for perfectionist persons, some things are not full natural yet. For use as a restoration tool, it require more advances and reduce costs even more, to allow add the color details, the little hue and saturation variation in relation of the 3D shape of obejects in relation to some light source in the set.
For example, the only colorized video I ever saw that put some color cheeck (warmer than the rest of face) was the colorized clip of The Flying Deuces. Skin color it's none of the major challenges with colorization, cause colorization uses a color spectrum. They set a object (like skin of a character) and add a color to each gray tone of the skin. This is often not enough to get a full natural look, cause human skin have many color tones.
I like some mpdern colorized films, and enjoy to see the technical advances happening.
RayPointer wrote: " Again, this is due to the lighting for black and white, which is different than what was used for Technicolor. This is not to say that effective colorization cannot be done. The existence of a full gray range should actually be an aid. The technology continues to improve. With respect to the purity issue or to colorize or not to colorize, the technique can be looked upon as a means of reconstructing otherwise lost color sequences that exist only in black and white. If production records or fragments exist showing the original colors, this can be a tool to truly restore the film to its nearest original representation. So for this, I see Colorization as a valuable restoration tool.
Keep thinking...