Thanks Dune.
Yes, I started with the colors, I built maybe twenty or thirty 512*64px colour maps of various greens/yellows and browns. (I had maybe five of these already from a grass file I downloaded a long time ago). I then went to TurboSquid and searched for grasses, picked out a few I liked and copied them. (Was easier than searching google for real images). The color maps are very convenient, as they can stretch in the vertical for stems, or with an opacity map placed under them can become thin leaves.