The sequence Esc & b # M can be used to:
"specify whether to print using the current rendering mode or a fast grey-scale equivalent. Pages printed using the latter do not use any colour, and therefore print faster and more economically".
Use # values:
0 = Print in mixed render algorithm mode
1 = Print using grey-scale equivalent
I don't know which devices support this sequence; from the description I'd guess it may apply only to InkJet devices, not LaserJet (but I may be wrong).