In my experience, anything can change the colour of coloured leather especially if there's an underlying stain. Usually the leather will look patchy when you apply the product but will dry back to uniform colour. That isn't to say the colour won't change, though! To be sure not to change or lift colour, use solvent free products. The plus side of using a sprayable prduct is that you'll be able to apply a thin, even coating with the least risk of changing colour. Some leathers don't take well to spray products, though: I have a polished calf leather bag which got horrible droplets on the surface from a spray but luckily I was able to rub them off with a microfiber cloth. The downside of gels/lotuons is that it's not easy to apply an even coat especially if the leather has dried up. To sum up, the safest for your bag is maybe to use the spray first and then make sure your bag doesn't dry up in the long run
