Matt94GT said:
Blue = Burning Oil
White = Condensation or a good sign of blown headgasket
Black = Carbon or Running Rich
Red = Your car is one of a kind
There's actually a fuel out there that burns a reddish brown, It was a big deal like 2 or 3 years ago, I remember a lot of people using it, including one of the guys at the shop. Don't know who made it, it might have been a VP, but i'm not sure. Anyway, it looked pretty cool. I'll try and find a picture.
White smoke can also be buildup in the engine burning. I remember replacing a set of injectors a long time ago on my old LX, and finding a couple that weren't working anymore (one had a dead spider in the end of it ?!?! :dunno

After I put them in, the car smoked white for a while until it cleaned itself out. The same is true if you've ever used SeaFoam, It makes your car smoke white because it's burning a bunch of crap. So in reality, we should say an excess of steam coming out of your tailpipe would indicate a blown HG, as would the loud, exhaust leak-type sound.
Fets- If you stand on the throttle, and black smoke comes out, you are running rich, unless you are just moving a ton of air through the engine. In high horsepower cars, you will often see smoke coming out, even if the car is running lean, just due to the large amount of air and fuel that are being burned.