Basically, the default grass emitter, but instead of green, it takes on the color of the brick it's being emitted from.
Not sure if it's possible, but you could just recolor the default grass emitter to be multiple colors.
The coloring scheme has been done many times with other emitters. This is very possible.
I mean recoloring it on the spot based on the brick color. I know recoloring an emitter is possible, that takes five seconds. What I'm not sure about is having the emitter recolor itself according to the brick.
LaserA does this.
someone do it
Almost forgot about LaserA. :D