If they are pretty dry and brown when you cut them. Call em a brown or carbon material.

Another way I like to decide if something is green or brown. If you make a pile of it all on it's own, would it start to stink? (hay or grass clippings if allowed to be in a moist pile will smell. Leaves or straw tend to do little in a moist pile all on their own.)

The difference is kinda like this. The growing grass before going to seed usually has a higher nitrogen content so grasses cut before going to seed (like hay) are concidered green. Grasses that are grown for grain are allowed to mature and the nitrogen or protein has moved to the seeds and out of the grass stalks making the stalks a brown or carbon material (like straw). Truth is most of this has only a little to do with color, that was just someone's idea of a way to make composting easier for the masses.

tclynx: Very insightful. Where did you learn that about grasses? I don't think I've ever seen that on GardenWeb.

There has been discussions about hay vs straw on here before. It usually crops up when some one mis speaks and says they are using hay as a brown. Or the other place it really crops up is when people try to figure out what the grass clippings become if they dry them out.

Here you go - lots of previous discussions on whether dried grass is a green or a brown. ;) Just scroll down to the discussions with the blue borders.

Dave

Here is a link that might be useful: Dried Grasses - green or brown?