Quick question about soldering a motor & grinding a flat rotor spot.

I realise this is a bit of a newbie question, but I have to be sure. I was wondering about the 3 colours, white black red. Exactly where does the red one go, and the black one? Is there anything WRONG?

And also, I'm not sure what to search for exactly, but how do I grind a flat spot on the rotor shaft for a pinion? What's the best approach to doing this?