I love the smell of UnrealEd crashing in the morning. – tarquin

From Unreal Wiki, The Unreal Engine Documentation Site

Draws a material onto the entire screen.

See CameraEffect for instructions on how to use the camera overlay and other camera effects correctly.

Properties

color OverlayColor 

Color of the material to draw. Use white (R, B, G and A set to 255) to draw it in its original colors. This works exactly like the Canvas DrawColor.

Material OverlayMaterial 

The material to overlay.