This is one thing worth mentioning. A lot of people beat themselves over the head with this one. I’ve lost count of how many lengthy, and I mean LENGTHY, debates there have been about whether your costume should look like how it did on screen or in person.
Stage Hand: Cows don’t look like cows on film. You gotta use horses.
Martin: What do you do if you want something that looks like a horse?
Stage Hand: Uh, usually we just tape a bunch of cats together.
So in Aliens, the whole film was shot under blue light, so they colored the props accordingly. The Pulse Rifles (as well as other props) were painted a shade of brown to make them appear olive drab on screen. Armor was lighter, but looked dark on screen. The Aliens were given brown highlights rather than blue. Some people prefer to make their costumes so they look like the actual props, others prefer to go with how they look on screen.
Ultimately, it’s down to you which way you go, this is just a heads up so when you see a brown Alien, you don’t go “WTF?!?!?!”.