The military system of assigning a colour to an alert - red alert for example.
This system is used on most military bases and in their operations. Black is the lowest alert, red is the highest. A denotation of 'special' indicates that personnel should be more vigilant than they normally would at that alert state. This is typically found when circumstances - such as the troubles in Northern Ireland for a UK base, or a general election - are in place, which, although they do not directly threaten the base, could cause base security to be compromised.
This system was made so famous by Star Trek and other programmes that the term 'bikini' alert has passed out of popular usage as the system becomes part of corporate consciousness.
In the UK, the system is as follows:
- Black - the lowest alert state. This is used in 'normal' circumstances.
- Black Special - used when circumstances may be a concern. The continued threat of the IRA in the UK means that this is the alert most often seen in UK military bases. It has also been used more often since the terrorist attacks of September 11, 2001.
- Amber - a heightened state of alert, often used in times of war when there is no direct threat to the base.
- Red - the highest state of alert, used when there is a direct threat to the base. When Bobby Sands was killed in Portsmouth, the naval bases there were on red alert.
Of course, Star Trek altered this system, but the basic principle remains unchanged. As far as I can tell, the Star Trek system is as follows.
With thanks to the Ministry of Defence, Teiresias and the Stationery Office.