The pink/orange toilet stains are likely Serratia marcescens bacteria. These bacteria are most common in toilet bowls, shower stalls, dishwashers, tiles, sinks and pet water dishes.

Any damp place with phosphorus or fat will develop the bacterium. Serratia can grow in toilets where water stands long enough to evaporate chlorine residual disinfection. Chlorinated water kills Serratia and bleach removes microorganisms from toilets.