Here is a pantone color I found that's very close to 918 orange.

https://www.pantone.com/color-finder/717-C

Here is a comparison to my car. my paint on the left and pantone on the right, also with a couple of other pantone colors below.

Here is the picture that I cropped for my color. As it is original paint behind the tail light finisher there is no fade. I took the picture with no flash in natural light, overcast sky, not direct sun.

 

I found the pantone color 717 C, after a few tries here:

https://www.pantone.com/color-finder

 

Something I found.  Has some cross-references. Seems to be based on paint chips.

http://paintref.com/cgi-bin/colorcodedisplay.cgi?ditzler=60636&rows=50&syear=1970&smanuf=Nissan&smodel=Datsun&sname=Orange

And another link, with more links inside.  Looks like Wick Humble's book writes about it.

https://www.zcar.com/threads/where-to-find-datsun-orange-paint.74424/

Edited April 3, 20214 yr by Zed Head

And because looking at orange Z pictures is never boring...

https://bringatrailer.com/listing/1971-datsun-240z-165/