NASCAR Racing: Flaga, flagger, yellow flag

Question
Under the last caution in Sonoma the flagger was waving both the yellow and blue flag. What does this mean?

Answer
Hi Nikki,

The yellow flag obviously means that the caution is out on the race.  Very few people know this, but the blue flag tells the drivers that a wreck or something like an oil leak happened right in that part of the track, so they need to be careful.  So it basically is a "watch out right here" flag.

Hope i helped!
Coy Jordan