Brings back memories - I had a '69 Caprice coupe just like that except it was Fathom Green with a black vinyl top, 427, loaded to the gills, Comfortron A/C, etc; it was like a Cadillac with Chevy emblems on it.
Yep, the first gen Caprice rode like a true land yacht, but handled better than most of the other big cars of that day, IMO.
Another possibility that appears closer to that Caprice shade to me is Lemans Blue Poly. a bit lighter than the very dark Dusk Blue.
here is a link that has color charts and codes...
That's the problem with charts, hard to tell. I was going more by other pictures of dusk blue on the web. It's looks lighter on a car than a chart.
But when you consider how Gary's pic has the car in the shade, it makes it even harder to tell.
I'm glad to see the darker blues and greens trying to make a comeback in the new car world!