The uniforms were olive color according to the Star Wars Costume book.
From what I’ve seen of behind the scenes photos and such, this olive color seems to be accurate. Certain lighting may have changed that slightly in the final film, plus 35mm film tends to go a little bit green in shadowy areas, but I don’t think it’s anywhere near the deep green that I’ve seen in a lot of restorations here.
If you work under the assumption, as I tend to do, that they weren’t trying to do weird, unnatural looking things with the colors, then you can correct Death Star walls to look mostly grey, and low and behold, tarkin’s uniform comes out looking olive.