Bruce, as you know, the old colors do have depth, especially with "Clear" in the base. Scott Sloan's Stone Grey Speedster is beautiful and shows both depth and retro. The same can be said of John Leader's Slate Grey, thick and deep.. I get many positive comments on my original code Ruby Red with clear in the Glasurit. I also like the colors on Rick Davis' and Dan Palmquist's cars.
I do like the Seal Grey mentioned above... my engine tin is done in Seal Grey. But if you are seeking a truer original color, then an original with clear would be my pick (like Slate). Both the Seal Grey and Guards Red are newer colors.... and are nice, but may not reflect the period look you may (or may not) seek. There was a beautiful Seal Grey IM Vert D (Roadster) in the 356 Registry's magazine earlier this year. I can take some outside shots of my engine tin and send them to you.
A great place to get 356 color samples sprayed and sent to you is Wilhoits. They are listed under vendors on the 356 Registry Links. Two other SOC members have used them and were pleased with the samples. Look at a resto Speedster in Wilhoits list with Slate Blue... unique and beautiful. It is like Seal, with a low blue hue.
I had black on my VS.. it is classy.. and probably exudes the Speedster look better than anything other than silver. But it is hard to keep up. Swirl City without a lot of elbow grease.