I have heard that when a fish comes in contact with the signal if it isnt directly in line (straight down...centered) the arch could be tailing off either right or left, depending on which side of the 'ducer the fish is on. Also heard the reds and yellows say the fish is directly underneath where monochromed colored arches means it's within the reach of the signal, but not directly undermeath it sending a weaker signal. Might not be right...but it sounds like it makes a little sense.