Believe today the restorers are using a dye to reproduce the original look. Had a couple of quarts of the stuff around the house before the last move. Can't recall the supplier or the fancy name of the stuff.
There are multiple options for chromating these days, it can get a little complicated and the terminology can be confusing. There's the old process, which used hexavalent chromium, which is now identified as a hazardous substance and is not allowable for RoHS compliance. That doesn't mean it's not available - just that most companies are not going to use it in commercial products. Hex chrome over zinc will give the nice yellow finish we're used to seeing.
To replace hex chrome, trivalent chromium is now being used. It can give either a clear (bright silver) finish, or a classic yellow. There are different proprietary methods for achieving the yellow, however. Some use a pigmented solution (which may be where the "dye" reference comes in). Some topcoat with a yellow color. And some use a process that will finish yellow without pigment or topcoat. The trivalent methods do not necessarily provide the same level of corrosion protection as hex chrome, however I have read reports that some do and that the technology is improving in this area.
Briefly, zinc (or cadmium, in the past) is used to protect steel. It provides sacrificial protection from galvanic corrosion. Chromating is a top barrier to prevent the zinc from corroding. a sealer coat can even be applied after both of those to provide further protection, but I don't believe this was used on automobiles of the vintage we've dealing with. For driven cars or those in humid climates, corrosion protection is an important consideration when selecting a refinishing process. For those in arid climates, appearance may be the only consideration, and a coating that has the same cosmetic appearance as the original may be a legitimate choice.
