I have noticed a marked sameness about the answers that were posted. "You need to paint MUCH lighter than you normally would" and "always use contrasting flock" pop up almost on cue. So I've been moved to provide my views on this, even though I once did a post on nothing but my 3mm painting philosophy.
First off, you don't NEED to paint in any style, least of all in a style someone else thinks you ought to. Militaries, from time immemorial right up until this very minute, use differing shades of the same paint because they use multiple suppliers. No two vehicles have been exposed to wind/sun/rain/heat/humidity for the exact same amount of time. No two vehicles have had the same amount of time pass since their last overhaul and repaint (anytime a vehicle has major work done on it at the motor pool, it always gets repainted before it leaves).
Most wargamers (and indeed modelers) want to get as close to reality as is feasible with their painting, terrain, etc, and I'm no exception, but I'll be the first to admit that 1/600 scale minis do benefit from a slight "tweaking" of what the full-sized vehicle would look like in reality. The same can be said for 3mm terrain, including vehicle bases.
Let's be honest. These things are damned small! And they're small so that large games can be played at 1:1, or close to it. In a large game with a large table, I can get an entire 1:1 division on the board without crowding. So, "table loss" is a reality here. At 4-6 feet away, with realistically colored terrain and bases, you definitely can lose quite a few of these suckers on the table. So, going a bit lighter with the paint colors and the shade of flocking can definitely have a beneficial effect. A bit!
However...I can honestly say that I have seen other folks' minis which seem to need "Ringling Bros" painted on the sides. Virtually neon circus wagons. Now, to be sure, those folks should paint in a style that pleases them. Whether I like it or not is immaterial. Whether it looks even vaguely realistic or not is also immaterial. If they like it, that's all that matters.
I, on the other hand, like my vehicles to be closer to REAL reality. Sometimes I hear that my paint doesn't provide enough contrast and that my flocking is too close to the color of the vehicles. I disagree. The whole purpose behind painting military vehicles is to help them blend into the background (along with helping to protect the metal). I use a shade of flocking that is just slightly lighter than the vehicle. I want what I paint to be as close to reality as is possible without losing too many things on the tabletop. I go slightly lighter on the flocking shade I use, but I'm NOT going to use flock that makes it look like my vehicles are on the fourth green at Pebble Beach! I also give each vehicle a bit of bright, but historically relevant color ("bling").
So, as this is my blog and therefore it's about my opinions, I'll say that the knee-jerk "paint it way lighter" neon minis I see do NOT look even vaguely like real military vehicles. If mine are too dark and too realistic and don't have enough contrast to make them "pop", they're that way because that's what's realistic and I'm good with that. So can we get the game started now?