Glad you got in touch with ray, and he responded to your questions.
The reason I thought lilac, was a few years ago I looked at a lot of darker silver greys to use on a car I was painting, and noticed they had a newer tungsten grey mustang, and it gave a cast similar to that truck in the sunlight, and it had a bit of lilac pearl in that color. I ended up going If I understand you right, it is a lilac with silver pearl added, wouldn't have guessed that, but does make sense how it appears silver in areas the light hits. I haven't done a lot with custom colors, usually only shoot what the paint store mixes up for the code I give them.
Guess you have a few test panels to shoot, but if you do go with a custom mix, right down everything you did and used to make future repairs easier.
If you get in touch with ray again, you should tell him to head on over to this site and sign up. Looks like he has some neat cars (and a nice truck).