Instructions
Load the game disc on your console or PC and select "Multiplayer" from the "Call of Duty 4: Modern Warfare" main menu.
Select "Options" from the Multiplayer menu and then choose "Brightness." It is common in "Call of Duty 4: Modern Warfare" for the Multiplayer maps to have a reddish tint when the brightness is set too high.
Move the onscreen slider to the left to tone down the brightness of the game. You should notice the red fading out of the screen the lower you go. Once you find an acceptable setting that eliminates the red, press "Back" twice to return to the Multiplayer menu.