If all you want is monochrome printing, check your desktop computer's printer settings. I have seen grey printing options in my Epson and Samsung printer drivers.
I'm not sure that there is an easy way to do this in the App Inventor sources right now. We are planning an update to the latest version of Blockly, which supports themes, and my guess is that they are using a theme to accomplish the black and white drawing.
thx dr ayman but please how to return to my coloured blocs because all my programs became black and white.i think i have to copy and paste the original code (coloured blocs)
help please
thx
hi please i paste a code in blockly.css file to get a code black and white of my appinventor program to print it but the problem that all my programs become black and white and i don't know how to return to coloured program
help please
thx in advance
yours trully