Hi,

yes, Marklin made blue cars also after WWII.

From the 1949 0-gauge catalogue:


In the poor years after 1945 Marklin used every enamel which could be reached. But for my eyes that car is to "bright" and to "fresh" to be original. Also the Marklin-stamp on the bottom is missing.

But above the pressed Marklin-bike on the bottom you can see a shiny field, just where the Marklin-stamp should be. Original cars were stamped and afterwards the stamp was secured with a transparent varnish. In this case this field looks for me like a black resprayed surface where the the original securing-varnish looks through:


I share your doubts.

Regards

Markus