Well, here's a freebie for their data: I NEVER looked at the light on the gun NOR the targeting reticle to determine the color of last portal I had fired. Sure, it made for some misfires, but I mainly just took to firing one or the other in certain situations, and then rely on reflexes when I need both in rapid succession. Needless to say, I'm not the best portal player, but I imagine the good ones don't look at those indicators either, they're just better at remembering which one they need to fire.