Even in smoke, the crosshairs of turrets turn red when around you, so you won't be as well protected, but you still have opportunity for causing confusion.
A good tactic for smoke grenades is to use them as a diversion. Throw one or two smoke grenades at an often used staircase or choke point and have your team move in (recommended Improved Stealth) from another direction. Enemies often respond to smoke grenades with frag grenades or concentrated LMG fire. Another tactic is to smoke behind the enemy front lines, in places where movement is expected. Any Snipers looking down range will spot enemy soldiers a little more defined in the smoke, making easy targets. Although using smoke in an area where Snipers inhabit can be frustrating to the Snipers in question, when used successfully it can be an invaluable tactic for the front lines to push the opposition back.
When repairing, it is always good idea to toss a few smoke grenades around the object you're trying to repair. (especially gates.)
Also, in the event that you are parachuting in or get within range, you could pop a smoke grenade on top of a bunker and drastically reduce the chances of the turret killing your teammates, though the crosshairs will still turn red when targeting an enemy player, as stated before.
Poison Gas Grenades are sometimes used as more dangerous variants of these sometimes, because smoke grenades are unavailable, sometimes deliberately to prevent people from going through it to look for whoever threw it.
Another tactic is to deploy some smoke grenades when placing anti tank mines down to reduce the chances of a sniper killing you, as you are especially more vunerable when you are placing mines down.
The Smoke grenade looks the same for all three factions.