So after putting it together, I started to think in depth about the colors I will use. I really love the idea of having a dark imposing fortress. I originally thought about painting it a black, but the difficulty of accent colors and shades on something so large would be........complex to say the least. What I am looking for a is a quick a dirty overall color.
What I have come up with is I feel will turn out effective. I will base paint the fortress black, and then I was looking to use a Krylon spray paint of a dark green to lightly spray the fortress. By spraying as light as possible I plan to allow the black undercoat to peak through the dark green. This way I can also use GW's Dark Angels Green to highlight raised portions and edges of the Fortress.
This is the color I plan to use from Krylon:

Now I had trouble trying to decide what kind of secondary color I want to use on the columns and the Angel on the tower. I have debated using the GW Dwarf Bronze with Shining gold as the highlights, as well as some boltgun metal here and there. I will also be painting the skulls at the base of the tower in the same style as the skulls on my Khorne champion (base paint bubonic brown, then bleached bone, flesh wash, then dry brush skull white). Let me know what you guys think! I have classes starting soon so it will be awhile before I start painting, and I want to plan the painting down to the tiniest detail. Some ideas would be nice!
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Adeptus Astartes Commandments
1. Thou shalt not replace the Librarian's staff with a magic wand.
2. Though shalt not refer to thine brethren, whom the Emperor has dictated be armed with an incendiary weapon, as a "Flamer" constantly. For this has been proven to lower morale and cause strife within His Most Holy showering facilities.
3. Thou shalt not follow a Librarian around thinking, "Can you hear me now", repetitively in an attempt to drive him insane.