I tried to read the colour code, but it's faded. I got it from the original owner and I don't think he got it repainted. The shop seem to think it's silver originally since the firewall is silver.
I don't see it on this list of paint code. Maybe it was a dealership option back then and they just painted it whatever color you wanted maybe?!?!
http://www.datsun.org/roadster/resources/paintcodes.html