I was playing Battlefield 2 Modern Combat on the 360 last night, and was having trouble picking out the enemies on the maps.

I got frustrated in the first sniper mission, so I decided to quit out and try later. I looked through the options and found a Color Blind Hud and turned it on.

Two minutes into the map I achieved the Marksman Achievement.

I can't tell you what the difference is between the two HUDs...but it definately helped me whatever it was.