Command: bk_color
  
Syntax: 
  include graphics.e 
  bk_color(i)
  
Description: 
  Set the background color. In pixel-graphics modes the whole 
  screen is affected immediately. In text modes any new characters 
  that you print will have the new background color.
  
Comments: 
  The various colors are defined as constants in graphics.e
  
  In pixel-graphics modes, color 0 which is normally BLACK, will 
  be set to the same {r,g,b} palette value as color number i.
  
  In text modes, to restore the original background color when 
  your program finishes, e.g. 0 - BLACK, you must call bk_color(0).
  If the cursor is at the bottom line of the screen, you may have 
  to actually print something before terminating your program. 
  Printing '\n' may be enough. 
  
Example: 
     bk_color(BLACK)
 
See Also: 
  text_color
  
