REPLACE COLOUR                                                     <Alt>+R

  This function is used to replace a specific colour in a block with another
  colour. The colour under the cursor when the operation is invoked is the
  colour to be replaced. The current colour value is the colour used for the
  replacement.

  Use the arrow keys, <Home>, <End>, <PgUp> and <PgDn> to resize the box
  specifying the area that will be effected. <Tab> toggles between the top
  left and the bottom right corners when resizing. <Enter> completes the
  operation causing the replacement to take effect. <Esc> aborts the
  operation leaving the screen as it was.

  Normally, only characters whose background AND foreground colours match
  the colour to be replaced are effected. However, you can use the <+> and
  <-> keys to change to one of the other two replacement modes.

  The first of these two methods effects any colour (background or
  foreground) that matches the foreground of the colour to be replaced and
  replaces it with the foreground of the replacement colour. The second,
  effects any colour that matches the background of the colour to be
  replaced and replaces it with the foreground of the replacement colour.

  Note that in certain situations, these last two replacement modes won't
  work - namely when a background colour needs to be replaced with a bright
  colour. In these situations, the corresponding lighter colour will be
  used.