Extinction: camouflage on guns!
There is a way to get gold camo on extinction mode. You can do it by finding a suitable attachment for your weapon (not the pistol) and getting it. Once you get an attachment, you should notice your gun changing camos. If you didn't get golden camo, search for more attachments and keep swapping until you get what you want(gold gun with preferred attachment).
Extinction mode: Survival Guide
To make it out ALIVE on this game mode is simple if your teammates cooperate. Your team might want to have their stuff to look like this:
-Weapon Specialist(2x), Medic, Engineer
The Tank class is a very selfish class since it only helps 1 person out...so we're excluding this class.
You all need to cooperate on certain stuff too.
These are helpful once you all arm the Nuke since the vultures will take out aliens in your path and if placed properly, the sentries will use their fire power to take out some if not all aliens. I would suggest placing 2 sentries where the barrier hives used to be BEFORE arming the Nuke.(you can get 2 sentries if you upgrade them to level 4 with the skill points)
There WILL be meteors blocking your way at the barrier hive spot so once you get to one, set 2 of these babies out
From time to time, your team might go down, so you might want to have 2 people with "feral instincts", 1 person with armor, and one with explosives. Once you all arm the nuke, you will need to run for your lives because there will be 3 rhinos after you and running fast with feral instincts will be a must. Armor will protect you all from hunters and scouts that you encounter while running for your lives.
The extra powerful weapon doesn't matter, but I suggest all 4 of you get Death Machines since the barrier hives will take some time to clear. Death Machines, however, make it quick.
The only way to make it to the nuke is by upgrading the CLASS slots all the way, upgrading the FERAL INSTINCTS/ARMOR all the way and the VULTURE/SENTRY all the way. It doesn't matter if you upgrade the ammo or pistol all the way, but you will eventually run out of ammo.
Unlock Extinction Mode (Alternate Way)
Another way of accessing this feature is by playing Multiplayer Career mode and reaching level 5.
Unlock Extinction Mode
This feaure becomes unlocked at the 'Main' menu when you start a game in Single-Player Campaign mode on the Regular or higher difficulty setting and then complete the 'Ghost Stories', 'Brave New World', 'No Man's Land', and 'Struck Down' missions.
Start Chapter 1, 'Point Of Contact' in Extinction mode and collect a sniper rifle. Then shoot an 'L', then an 'O', then another 'L' on the 'Gil's Lodge Motel' sign to start the Golden Aliens easter egg where any alien shot will explode into golden alien stuffed dolls, this will last for ninety seconds and can be repeated.
In the "Extinction" level, head to the motel with the words "Gil's Lodge Motel" on its side. Shoot the sign's letters in the following order: L-O-L. Those letters will appear at the middle of the screen if you did things right, and an alien effect will take place for the next minute or two. You can repeat the process if you like.
Campaign Special cutscene
If you manage to beat the campaign on any difficulty and go through the credits, you should see a cut scene that was described by your father in the beginning of the campaign about the way the federation makes a ghost crack.