Something you might want to check into.
Some of the Saturns had bare primer insulator (like on the Shuttle External tank) on the surface beneath the booster stage (before the engines).
So the underside would be a rust-red muddy texture.
My brother (an Ex-NASA Engineer) corrected me on that when I was in my late-20s (while he was at NASA).
And some of the Boosters had a greenish primer/insulator.
Edit: Apollos 15/16 - 19 (This is the bottom of 18 you see here) had the green bottoms.
Apollo 11 and at least 12 painted the bottom of the rocket white (so if you are doing Apollo 11 mission, then you would have it right).
But if you are doing a pre-Apollo 11 (Apollo 4 - 10), then you might find either Red or White, depending upon the news coverage (only 10 was really known to have News Coverage, because that was
SUPPOSED to have been the first attempt at the moon, but they lost it on lunar insertion).
As for 12 - 16.... 12 would have been white or Red, 13 would have been red, and the rest I am not sure of (I would need to run down to Johnson to check the photos).
MB