IF your desired impression is that of a SWAT assaulter, then navy blue (better choice for low light conditions) or black will work just fine. However, as everyone so far has pointed out, unless you are doing very close quarters/room clearing stuff, wearing all black will make you a walking, talking (calling "HIT" a lot), bb magnet.
I should know...right Tankdude??
At any rate, the advice re. green/green-ish already given is sound, especially if you wish to remain mostly hidden within the foliage, or tan/brown-ish for more barren dirt-type landscapes, but there's nothing really wrong with black if that's a "look" you're going for. Just don't expect to live overly long out there. Or, consider it a challenge to stay alive despite what you're wearing...