What do the different color racing flags in the Indy Racing League indicate?

Green - Start of the race, qualification, or practice. Also used for restarts. Black w/ White Cross - Driver disqualified. Yellow - Caution. White w/ Red Cross - Medical on course or needed. Red - Race stops. Red & Yellow Stripes - Slippery track. Black - Driver must go to the pits. White - Final lap. Blue w/Yellow Stripe- Passing flag. Red w/ Yellow X - Pit closed. Checkered - End of race.