Here you can see this excellent tutorial "Painting Instanced Objects" and make grass with group of object and particle system:
http://www.blendercookie.com/2009/02/18 ... d-objects/
Or, you can complicate your life with this method (convert particle "string" to mesh) in Blender 2.49:
1. Make your particle grass
2. Convert the particle system into the mesh (in modifier tab)
3. In edit mode select all vertices and go to Mesh/Scripts/Edge to Curve
4. Now, select this new "bundle" of curves and go to Edit mode (delete mesh, we do not need it more)
5. Assign the thickness of the grass with Bevel Depth
6. Deselect all vertices and go to Select/Select/Deselect First
7. With ALT+S go to 50%
8. Add next vertice with Select/Select Next and go again (You have now two vertices per one "string") to 50%
9. Convert Curve to mesh and this is it
My english is not so good but I hope you can understand this short tutorial
