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.