Tutorial Forcing Grayscale Printing
At the time of this writing, this will only work in Chrome 18+, but it's standardized so support will eventually come to everywhere.
@media print {
body {
/* IE4-8 and 9 (deprecated). */
filter: Gray();
/* SVG version for IE10, Chrome 17, FF3.5,
Safari 5.2 and Opera 11.6 */
filter: url('#grayscale');
/* CSS3 filter, at the moment Webkit only. Prefix it for
future implementations */
-webkit-filter: grayscale(100%);
filter: grayscale(100%); /* future-proof */
}
}