Road courses work a little differently for various reasons, and the SCCA has its own set of rules and customs. If you are racing curious but don't know the flags or only know pro series or ovals, here is how it works in the
Sports Car Club of America
Blue (with yellow stripe)
Passing flag. You are being overtaken by a faster car. Don't be a dick.
Standing Yellow
Passing is not permitted from the station displaying the yellow until the incident is passed, or until a station not displaying a yellow is passed.
Pay attention; something has happened that requires paying attention.
Note: a standing yellow is often (usually?) a precursor to a waving yellow. Fools rush in...
Waving yellow
Serious incident after this station. Same rule as Standing yellow, no passing.
Use extreme care and back off from racing speed. Incident may impinge on racing surface.
Note: for incidents that take time to deal with, Waving yellows may be downgraded to standing yellows. This allows a waving yellow to be brought out usefully should another incident occur. However, for protracted incidents, a full course yellow is likely to ensue.
[Recent social media discussion of bad behaviour at Thompson was in part about drivers who passed under yellow flags while track crew was dealing with a fire adjacent to station one.
As a tech inspector, my time in hot areas is limited, but there are many workers, many of whom are friends of mine, whose work at the track is almost entirely in hot areas, and anyone flouting the yellow flag rules puts them at risk. Worker compensation is usually lunch, a beer party and maybe a gas card. Only dicks put them at risk.]
Double yellow
Pace car on track closing up the field. Use care near the incident (waving yellow will probably still be displayed), Use the clear track to catch up with the pack. Laps and race timer continue to count down.
Black flag
Two common usages:
Black flag directed at a single car - you have done something bad. Come into the pits where a steward will be happy to discuss it with you. Blow it off at your peril.
Black flag all - the stewards want to clear the track. Usually happens in response to a serious incident, while a double yellow is already in progress, so simply follow the pace car into the pits. Lap counter stops, but race timer continues. Many races have a planned lap count but also a backup timer and this timer can come into play if there are many yellow flag laps or extended time under black flag all.
Meatball flag (black with big red dot in the center)
aka Mechanical Black. Something is wrong with your car, come into the pits. This includes sound violations. Don't blow it off. If you stay out when violating sound, it is likely you will disappear from the results.
Red flag
Two Usages
Shown at all stations on active track - everyone stop their car
safely off the racing line in sight of the flaggers at the next flag station. Race timer stops. Used in response to an incident so serious that everything must be stopped to allow focus on response. May indicate that the racing surface is almost entirely obstructed. Wait patiently for further instructions. The flaggers may show a black flag to indicate that the driver should proceed slowly and safely to the pits.
Under black flag all, with all cars already stopped in the pits, thrown to pause the race timer.
White flag
Two usages
Shown at a station on track - you are about to encounter a safety vehicle or some other slow vehicle (possibly an off pace race car) on track. Use care.
Shown at start/finish - one lap to go.
Red & Yellow Stripes
Used to indicate debris or fluid on the racing surface.
(Note how I restrained myself and didn't call this flag "British Car on Track".)
The actual SCCA Flag Manual
It may be found here (it's hard to find on the SCCA website). This is the 2012 manual, but as of this writing (late 2020) it's still current.
http://www.averillpark.net/SCCA/F_C%20Manual_revised11.11.2012_ApprovedCRB.pdf
