There was a lot of discussion on the original blue or black windlace & weather-stripping on a two toned deluxe blue interior in a different thread (Kinks in my windlace), but I thought I would re-direct that discussion back to where it might belong.
Tim is absolutely correct that Chevy made a blue rubber product. I was in denial that they went to such lengths 60 years ago, but when I pulled the door sill weather-strip retainer there was clearly the original blue color. It is a very good match to the darker of the two blue colors.
Original blue weather-stripping The exposed parts were sprayed black by the PO, but you can clearly see the orignal blue that was under the retainer.