I think you've got the right idea. The painting guide certainly isn't much help. I think the silver call-out is for the wheel parts and the tools along the top portion of that parts sprue. The take-away here is that, being a gasser type car, you can go with whatever colours look good. They call-out red for the rear axel, orange for the headers, silver for the front suspension, all just imaginative colours, and nothing that is factory correct or represents an actual car. You can quite safely choose any colour for any of those components that looks right or good to you.