I have a pair of medium brown shoes that are a bit flat and boring in colour. I would much prefer them to be closer to my chilli pair. I've tried polishing with chilli polish and leaving unbuffed overnight for it to soak in but it doesn't seem to change much after buffing. A fella at the Shoe Hospital said that colour is determined in the tanning process and there's not much you can do after that, and that their dyeing process is just like painting on top of the leather and will ruin any likelihood of obtaining a patina overtime. Similarly I have a pair of dark burgundy shells which I try to 'redden up' using oxblood polish as they look almost black in dim light, but again, to little or no avail. Am I wasting my time here and should I just accept them as they are? Or are there some tips that can influence colour?