Image_Graph_Common | --Image_Graph_Line_Solid | --Image_Graph_Line_Formatted | --Image_Graph_Line_Dashed
This style displays as a short line with a shorter space afterwards, i.e 4px color1, 2px color2, 4px color1, etc.
Image_Graph_Line_Dashed Image_Graph_Line_Dashed( mixed $color1, mixed $color2)