I'm sorry to be late to the party but things have been very tumultuous at work.
I think what you see here is that, in the shooting of the footage of the show, they seem to use some to use some very powerful lights. I seem to remember reading that, early-on, in the making of the show, they managed to melt some of the rubber puppet heads just from the lighting. (I think, on SFXB, one of the interviews with the crew might mention this).
Now, that lighting seems to have a higher, goldish colour temperature (I would think about 2500K), meaning that your grey battleship takes on a faint but definite greenish tint in many scenes of the show.
However, when it gets set up for the publicity shot (the still image, where the fighters next to it show as being blue), it must get lit with a much more natural colour temperature, which is bit less flattering; closer to daylight colour temperature (3000K).
That way, you see that, in truth, it's just painted grey.
I agree completely with Felice, though, given that, in all the iconic scenes of the show, where you see it travelling in space, it has that green tone, I think I would be inclined to give it that green tone in the colour that you paint it.
I hope that that helps you in some way.
I'm really looking forward to seeing the finished outcome. I've gotta tell you.
How is everyone doing by the way?
I'm looking at it again...
It's really a khaki colour, isn't it? It's not even completely grey. There is a faint green element to both light and dark shades; nomatter which images you look at.
The yellow lighting that they seem to use for the space scenes; as opposed to the planetary shots that come slightly later in the show seems to bring the green out more.
Dream big and bold and daring.