ColorBug

Trojan.Win32.ColorBug or ColorBug is a virus that runs on Win32 Operating Systems.

Payload
ColorBug appears as an average executable, but the user will notice the .EXE file lacks an icon. When run, nothing will happen until the user reboots the system. They will soon realize the color palette has changed [colors are random]. However, the virus fails to lock display settings, so the user can quickly change the color scheme back to default.

It's not a very destructive virus but can be pretty annoying.