Black, Champagne, and Butternut Yellow were initially listed as RPO colors in early 1969 Chevrolet marketing materials, then dropped. They built a few cars in those colors and they are not designated special paint. Later in the model year they returned as "special order" colors essentially meaning they were extra cost; $12.65 I believe. Later cars in those colors are also not designated special paint.
The car in question is a later build and likely - - PNT because of stripe delete; the cowl area does not appear to have been trimmed in white. It would make for a really rare, sharp Z/28 but it would be quite a project.