Plan for localised stain on smooth leather 

1. shoe shampoo - this cleans and gets rid of loose colour. Giving the new polish a better chance of going on evenly
2. apply polish to the stain area to see if it will colour to match the surrounding area
3. if that doesn't work, I'd use a stronger  cleaner and or stronger colour
4. once stain is even with its surrounding area, polish both shoes all over