I'm just getting ready to start restoring my heater, and it's the greenish blue metallic that BLUEMEANIE posted
here.The truck is also a '51, built in Oakland and shipped to Alaska. The greenish blue color is pretty pristine under one of the sleeve where the defroster tubes go.
Just another sample. I suppose they may have sourced the heater from Canada, though.
Here's a couple pics. I'll post up what I might find for a matching ratttle can color.