Probably been suggestion before but I'm too lazy to look. Let people customize their HUD for aircraft, infantry and vehicles. it seems right now the TR have the best color HUD because it doesn't blend into the lamndscape as much as the other factions. If you want an example of this, make a VS character, go to Esamir, spawn a Scythe and try to find your crosshair. I would much rather have the option of changing my HUD color to red or purple since those colors don't blend in so easily. Same goes for reflex sights for guns. The VS's holo sights can blend into the background. Summary- Allow players to customize their HUD, crosshair and weapon sight color.
At first I was thinking you were talking about the HUD of the game in general, should of made the topic "Customize vehicle HUD color" I totally agree though. Contrast and sight color are always a giant pet peeve of mine. I'm thinking of a game like Terraria where you had an option to change cursor color, I constantly fiddled with that because I wanted one that was noticeable in all scenarios. At the very very least they could easily introduce alternate sights for SC. Though realistically I would hope they would allow for at a bare minimum for crosshair color to be changed.
