Alerts should be designed so that the pilot can acknowledge the problem and suppress the alarm. According to the FAA, the system should automatically remove the alert when the conditions no longer exist, preventing a “nuisance.”
The FAA recommends manufactures use six or fewer colors.
Alert colours on the flight deck for future aircraft will have red warnings, amber or yellow cautions and any colour but red, amber, yellow or green for advisory alerts. Attention cues can not rely solely on color but must alert two senses.
Weather, terrain or traffic displays may still use the four colours, but “must not adversely affect flightcrew alerting.”
