The AOA lights

Some time in the 1950's the Navy, and later the Air Force, started putting AOA annunciator lights on top of the instrument panel to aid in holding proper angle of attack for landing. The top light tells you your AOA is too low (fast), the middle light tells you you're right on, and the bottom light tells you your AOA is to high (slow). The funny thing is the Navy and Air Force couldn't agree on what colors of light should mean what, so they ended up using different schemes. In the Navy scheme the light colors from top to bottom are green, yellow, red. In the Air force scheme they are yellow, green, red. So, in a Navy jet you want to see a yellow circle displayed while on final approach, and in an Air Force jet you want to see a green circle.