In cases where you want to turn off color printing, regardless of the use of color options in a rule file, you can issue this boj command.
boj {chr(27)+"&b1M"}
Should you want to apply some conditional logic to this, you can do so by setting a variable in prejob, and then using that variable in the boj command. For example, if you want to use -prm mono=1 in the unform command line to turn on the feature:
prejob{
if prm("mono",err=*next)="1" then monochrome$=chr(27)+"&b1M"
}
boj {monochrome$}