changing colours

hey guys,

Im busy going through the wikibook guide, http://en.wikibooks.org/wiki/Blender_3D:Noob_to_Pro/2D_Image%28logo%29_to_a_3D_Model

but I can’t figure how to change the colour of objects.
I finally found how to change the world colour, and there is a button before it which I think is supposed to be for whatever you have selected, but I changed silver to yellow and it didnt change in the preview or the render…

trying to change the bolt to yellow… http://img87.imageshack.us/img87/1338/untitledni9.th.jpg

>.< plz guys~~~ help me >.<

You have that Material set as a Node. Either click Nodes to use it or create a new material.

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