Never apply directly onto the leather, always apply with drops applied to a cotton bud or soft cloth and dab or gently stroke the cotton bud or cloth over the stains to be removed.
DO NOT RUB HARD.
As soon as you see the stain on the cotton bud or cloth, swap to another clean cotton dub or cloth to prevent the stain from being returned to the leather.
If you see the leather colour coming off, stop and wait for the surface to dry out, then go back and inspect the results. If all stains are removed now you can apply some leather protection cream to this area to provide protection again from future stains.
Do not use on suede, nubuck or absorbent materials.