This puts paid to 'those black and white days' and gives a good insight to the colours of the clothing, signs, street furniture, buildings of the day inter alia . What is more apparent is the lack of road traffic and Albert Kahn's Autochrome collection is far greater than shown here.
They are indeed a very useful source of research material as are any pre-WWII colour photographs and films. Although the photograph or film subject may not be exciting, however it's the background I find fascinating as I'm looking to see what's there. They also give an overview of social history.