Related Clues:

• 'Heads up!' and others
• Warning signals
• Mobilizing events
• Critical warnings
• Puts on the qui vive
• APBs
• Some computer messages
• States of readiness
• Notices
• APBs, e.g.
• Color-coded government announcements
• Colorful warnings
• Sounds the alarm, e.g.
• These may be red
• Urgent warnings