You normally only get that when the pads are down to the metal. Try an alloy wheel cleaner and when they are clean, wax them like you would the bodywork and that keeps them a bit cleaner for longer.
A product called Wonder Wheels is possibly the most aggressive of the alloy wheel cleaners.....brush it on, leave it a while then rinse it away.
Keep it off the brake calipers if you can!
John
The red comes from iron in the brake pads and discs. Since brake pads no longer contain asbestos, there are more metallic compounds in brake linings, they are also harder on discs than asbestos was.