The first thing you need to know is that this is on a naval base. The second thing is that it is (or was) a thing.
From 1970 to 2006, Bikini alerts were used in UK defence establishments to indicate the current threat level (red = war, amber = high alert, etc.) rather than the current bathing costume preferences of female personnel – although it would be interesting to know where the burkina might have fitted in, had it been put to this purpose.
The word “bikini” was apparently chosen completely at random by a computer. Yeah, right.