Heads-up and Red alert

Heads-up noun - The act or an instance of telling beforehand of danger or risk.

Red alert and heads-up are semantically related. In some cases you can use "Red alert" instead a noun phrase "Heads-up".

Red alert noun - The state of being constantly attentive and responsive to signs of opportunity, activity, or danger.

Heads-up and red alert are semantically related. You can use "Heads-up" instead a noun phrase "Red alert".