Pretty sure it's gray. This is from a '70 GS that is being restored. So it's not original but Rich Johns tends to get these details right.
They resto places sell it in spray cans. If you want "close enough", go get a can of Krylon Smoke Gray from the hardware store.
Is that the correct color grease on that control arm bushing? Just kidding. Looks great. I would like to see more of that chassis.