pencolor  -- Command, one input.  Abbreviation: penc
     This command applies only to the display turtle.  Its effect  is  dif-
     ferent depending on how each type of terminal supports color.  For the
     Atari, the input must be an integer between 0 and 6.  An  input  of  0
     enters  black-and-white  display  mode  (which is the turtle's initial
     mode), in which lines are as thin as possible but there is no  control
     of  color.   Any  other  input  selects color mode, in which lines are
     twice as thick, so the effective size of the screen  is  smaller,  but
     colors  can  be  used.   There  are, in color mode, three possible pen
     colors, numbered 1 to 3.  There are  256  possible  colors,  but  only
     three  can be on the screen at a time; the setcolor command is used to
     decide which pen draws in which actual color.  If the input is  4,  5,
     or 6, the color is that of pen 1, 2, or 3, respectively, but lines are
     drawn in "fill mode": for each point inked, all points  to  its  right
     are  also  inked until a point is reached which was already inked.  On
     the Gigi, there is only one mode, and there is no loss  of  resolution
     in  using  color.  The input must be between 0 and 7; 0 means black, 7
     means white.  The ADM, Tektronix, and Sun displays do not have  multi-
     color drawing.
