The AoA indexer lights are inverted on Arma 3, in Arma 3 the upper green light indicates speed is too high (AoA is too low), middle amber light is ideal AoA, and lower red light is too low speed (high AoA). However, IRL, AoA indexers work all the way around, upper green light means you're too slow, middle amber is ideal and lower red light means you're too fast, you can find this info on declassified flight manuals of several US Navy aircraft, including the F/A-18C Hornet A/B/C/D NATOPS publication.