Set line and text objects to Black or White.

  BLT is an M-file that will recursively change the color

  properties of the given object, or the current Figure window by 

  default, and its children to give proper black on white or white 

  on blackhardcopy output. The color of the line/text object depends

  on the contrastColor RGB triplet supplied, or the Figure's color

  attribute if none is supplied.



  Returned are the colors of all line and text objects found while

  traversing the tree of objects. This can be used to restore the

  previous colors to all line and text objects. 



  See also PRINT6ZA50LG.