Simplest answer comes in two forms:
First for is if there is no time to prepare, and that answer is by far the simplest.
WEAR WHAT YOU HAVE AND SURVIVE. Keep a spare change of "bug out" clothes in your car or wherever you go, or simply don't wear anything you wouldn't be able to survive a week in without changing (at least you pants). Camo patterns work best in the wilderness but solid colors work well in some situations, especially at night. (OD and Navy Blue, Black even at night will make you like a boner in gym class)
The second form of the question assumes that you have some time to prepare and can "dress appropriately".
Simply put, WEAR WHAT WORKS. If you are trying to blend in with the sheeple, wear what would accomplish this. If out in the bush, wear what works best for your area.
Obviously I'm not going to wear BDU's, not interested in being mistaken for the military.
First of all, most LEO Tac teams are now switching to some form of at least knock off military pattern as well. But this raises two questions:
First is, what are you so afraid of in wearing such? If it is other "preppers" going ape shit and shooting at you cause they think you are the gov. then treat them as hostile because they don't possess the IQ and plain common sense to IFF. And clearly such douche-baggery should be eliminated from the gene pool.
The second question is, could it be to your advantage to blend in with those who regularly wear such uniforms?