Hi Dann and everyone else,

Thanks for the reply. I've done what you said and the sphere is no longer green. But it seems it is just taking on the color of the blinn.
I am new to Maya and could be skipping a step or something. Here is a break down of exactly what I am doing.

1. Open Maya
2. Windows>settings/preferences>plugin manager>(check)mayatomr.mll
3. Close plugin manager
4. Create>nurbs primitive>sphere
5. 6 (to shade sphere)
6. Bring up hypershade window
7. Right click on create maya node>select create mental ray nodes
8. Render>render using>mental ray
9. MM drag dgs_material into the work area
10. MM drag dgs_material from work area and drop on sphere (which turns green)
11. Scroll tabs of the window above the work area to shading groups
12. Right click on dgs_material1sg>gragh network
13. Back to create maya nodes and MM drag blinn into the work area
14. Select dgs_material in the work area to bring up it attributes
15. MM drag blinn1 to surface material (sphere now turns grey)

Now if I select the dgs_material in the work area and change the color (diffuse), in its attributes, it stays grey. And if I do the same for the blinn, the color on the sphere changes with the blinn. And also when I click the render icon I am now getting the sphere in a jagged grey and black (see pic). I'm not sure why I'm getting that now, I have not changed any render settings.
Thanks again for the help!