i have received this error message - 1078: Label must be a simple identifier

function movePipesandLines(event:Event):void {

  pipe1.x = pipe1:x - 5;

  pipe2.x = pipe2:x - 5;

  pipe3.x = pipe3:x - 5;

  pipe4.x = pipe4:x - 5;

}

stage.addEventListener(Event.ENTER_FRAME, movePipesandLines);

// if you have any suggestions please let me know

thanx