The phrase "yellow flag" is often used to indicate caution or a warning. It means that something is potentially dangerous or risky, and we should be careful and think twice before proceeding.
Sentences with «yellow flag»
Eventually a nice yellow flag came out and we did our pit stop. (speedsportlife.com)
Even better, when a new message comes in, a little yellow flag pops out from the side. (cnet.com)