How do I get a Sphere in opengl to be the colour silver
Silver is achieved through material properties and a good lighting model, and is more than just a glColor* call. Use glMaterial calls to set up your objects material properties and have a look at some examples here: http://reality.sgi.com/blythe/sig99/advanced99/notes/node153.html
I believe Silver is listed in there.
You may want to add an enviroment mapping (a little bit) - to make it “reflective”.