Did Dark Olive ever change?

[davepl]

My Dad's truck, which he had since 1970, had always been this color. Matched the interior too I believe, so not likely a repaint that early in its life.

It was always a bit unique though. It seemed to have a lot more blue in it than the Dark Olive trucks I always see.

Any ideas? Sorry, the photo is not the best. It's a 1968 GMC 910. Weird truck - 307 but every HD suspension option. Power steering but manual brakes. No radio, but it had a lighter.