Color photography was developped in the thirties of the last century. The successful break through in popular photo journalism or in industrial usage started later in the forties. That's why we don't have any vintage color postcards on Greta Garbo.
Publishing companies in those years were clever enough to produce postcards which appeared colorful. Also Ross Verlag didn't want to do without producing such special cards. The process wasn't too complicated or laborious. Manual colorizing (hand tinted) gave the impression of a real color card although a lot of collectors consider them as kitsch because the manual color can easily look unreal or exaggerated.
Nevertheless Ross was ready to produce colorized cards. That doesn't mean that all Ross cards have been produced in that version as well. As additional service and for a little surcharge colorized cards could be ordered from the company. The dealers themselves could also order those special cards for their customers. It was a production on demand.
As far as I know there are regular Ross cards and luxury cards which have been colorized from time to time. I never saw a scene card or an art sheet that has been edited as colorized issue.
The only exception Ross made regarding those products was related to one special package of miniature collecting cards. As I mentioned before, pack number 432 was exclusively distributed as colorized edition (1937).