Thanks to all for the terrific feedback. Even if we don't have definitive answers, just knowing how others think through these issues has absolutely helped me and I hope it helps others as well.
Rick, thanks for your input. It is always appreciated when a vendor takes the time to provide thoughtful, concrete feedback... and I always appreciate full aerosol cans! To clarify, I am not trying to match to another paint brand and your point about the proprietary nature of your colors is completely understood. My goals are relatively modest (I think). All I want to do is get a light blue color that is in the same ballpark (admittedly a qualitative measure) as the current color in my dash and doors (or at least the parts that aren't worn down from, dirt, sun exposure, etc.) It doesn't have to be an exact match to what is there, as I will be repainting everything. However, I have applied three coats to the ash tray from one can of AP-5748 that I bought from NPD and it is (to my untrained eyes) at least 95% silver and at most 5% blue. I want to be able to look at my dash -- or even better, have a stranger look at it -- and immediately recognize that it is light blue. Right now, anyone who looks at the painted ash tray would say that I repainted it silver, which is obviously not what I want.
I recognize that perhaps NPD may want their light blue to have so much silver, which is obviously NPD's choice. It just means I will need to look elsewhere for light blue.
Update: Yesterday I drove out the NPD Ventura location (about an hour away) for the fourth time in two weeks (I just can't help myself!) to get some feedback on the light blue and pick up some medium blue and some other items. Re: the light blue, I brought in my ashtray repainted with the AP-5748 to show them how silvery it is but I walked away a little frustrated by that part of the conversation -- it was basically "we understand your frustration and basically agree that it is silver but there isn't much we can do..." However, I called NPD's 1-800 number and spoke with a very nice man (alas, I forgot his name) in NPD's Florida location, who offered to send me a new can of AP-5748 for free to see if a different batch will be less silvery, which was a great idea on his part. So I am waiting on that can to see if it is notably different. Fingers crossed.
In the meantime, I started using NPD's AP-5747 medium blue metallic for all of my darker trim pieces. I have a FB, so I have those large upper quarter panels with the vents in them, along with a number of smaller complementary pieces. So far, the results have been very, very good. Is it an exact match? Of course not, but it is certainly "close enough" and that is all I want. Now I just need light blue that is approximately close and I'll be flying high again in my restoration.
Dbenichou289, what a great idea to use the VP on the windlace -- that never would have occurred to me. Has the repainted windlace held up well in retaining its paint, given that it has to be stretched and bent pretty substantially to fit the doors?