actually i'd like to correct you...
blue smoke means burning oil... doesn't neccesarily mean rings
black smoke means an unthrough fuel burn... could be injectors, igition, you accidentally put in diesel (lol) etc...
white smoke means burning coolant... not just a cracked head... head gasket and a break in coolant lines in the TB could be to blame as well

my .02

 

I agree 100%

Worn rings will not scrape the oil out of the cylinders, causing it to burn in the walls. The 2 MOST COMMON problems associated with this are valve problems or worn piston rings. This burnt oil causes a blue color.

When you crack a head, blow a gasket, etc., coolant exits through the exhaust pipe, causing the smoke to appear white.
Again, a cracked head is the most COMMON problem associated with white smoke.

Lastly, unburned fuel exiting the tailpipe results in black smoke, many different causes, but I was listing the general.