It is not possible to completely prevent color transfer in dyed leather. This is because the process used to maintain the quality of the leather makes it difficult for the dye to settle and makes it more susceptible to dissolving in water.
To reduce color transfer, you can waterproof the item using a waterproof spray.
If moisture from rain or sweat adheres to the leather and friction occurs, the color will easily transfer to the area of friction. By using a waterproof spray, the water-repellent effect will repel moisture, making it less likely for moisture to adhere to the leather. This makes it harder for the dye to dissolve, which helps prevent color transfer.
Also, on days with high temperatures and humidity, it is recommended to avoid bright colored (white) clothes and wear dark tones instead. Although this is not a way to prevent color transfer, choosing clothes that will not be noticeable if color transfer does occur is one way to prevent this.