This was the feedback from MK that I had on colour transfer...
"If a denim item has transferred its colour to the bag, I would suggest you contact the retailer of the clothing item, as it is the one losing colour.
Regarding the bag I will advise to take it to a leather specialist and check with them if there is something that can be done.
Kindly note denim clothing is likely to transfer, which will be more noticeable in a light colour such as pale pink than a dark colour one.
It has nothing to do with the leather being treated or not"
Yes, that's the definition of color transfer.
Its a problem for me chick, half my wardrobe is smart denim!I will rain and stain, its the way forward.
If it has nothing to do with the leather being treated or not, treating it again won't help. Your denim isn't colorfast.