To print colored or grayscale bitmaps correctly to a black and white Postscript printer, you need to print to a Postscript Level 2 printer (e.g., LaserWriter IIf, IIg, LaserWriter Pro) and use a Postscript Level 2 print driver (e.g., LaserWriter 8 driver). If you print using an earlier print driver or printer, the bitmap will print as black and white. The colored or grayscale pixels will not print dithered.
This includes:
1. Color screen shots or screen captures,
2. Black and white bitmaps from MacPaint, HyperCard (and similar programs) that are subsequently colorized in MacDraw Pro.