Is there a mod to remove the Aliens green hud in multiplayer? I have been going through mp alone on every map and finding hiding spots for when my friends show near. But I don't know if it is a good place or not with the darkness around them.
No, but you can make one. Use Texmod (you can find multiple tutorials online) and find a texture that looks like similar to this:
(https://www.avpgalaxy.net/forum/proxy.php?request=http%3A%2F%2Fudn.epicgames.com%2FThree%2Frsrc%2FThree%2FColorGrading%2FRGBTable16x1.png&hash=a90e63f99e14303597d1093561f9e1680f7f6557)
And switch it for the one above. That should remove the overlay and leave it neutral looking.