well, the only reasonable explanation to that is that the movie has bugs (just like roy's heatshield was yellow when he entered into the enemy space ship to rescue hikaru & minmay after they were captured on a tryst at saturn:P), i have watched the movie again and noticed that scene hikaru flying 1s at teh side of bridge and nodding to Misa, the heat shield is red but the last scene right before he blew off the Big BRain, the heat shield was clearly black. (query where was Max at that time )
as for max, the figthing scene with Milia right after kakazaki was blown up, i think i saw a black heat shield. anyway i think it doesn't really matter, it is up to your personal taste, just like the Low-viz which never appeared in the show and yet has received wide popularity.