[Tengu]

I purchased some touch up paint for stone chips from Paintscratch in the US. I haven't applied it yet but it looks very close. Called guardsman blue poly. F (1964). And the small square of GB on the website looks just like my colour. There are a lot of comments on the subject on the Internet. I think if your going for a full re spray, it's not so critical, but matching sections is the problem. I think the suggestion to get a scan is a good idea, but better from a car than a photo. Not sure what equipment is used to do that.
If my car was running, I could have attempted to get a scan for you. Maybe try a local mustang club and see if anyone has a guardsman blue pony.