I'm making a sun and I would like it to be a mix of colors - such that every face has a different color, like on a ColorRamp. So, I want the final thing instead of just being a flat orange color to also have some reds and yellows merging in with the orange so it's an array of different colors. How can I do this in Cycles, by using the node editor?
While you can assign a different material to each face on your model, I don't think that will give the result you want. I expect you want to use some noise to get colour variations, one way is to feed the noise into a colour ramp node.
There are other noise textures such as wave, voronoi, musgrave or magic that can give varying results, you may even want to mix a couple together. Just experiment with the scale, distortion and detail values to get a variation that you like.