Water stains on leather are a quite common problem in case of soft aniline leather, especially on the light colours.
The pores of this type of leather are open and they absorb moisture that results in darkening of the surface of the leather. Such stains cannot be removed at home. Thereat it is important to ensure due protection of the leather.
In case of soft leather the problem is that it is rather difficult to achieve the original colour shade when re-painting it, but it is almost not possible to make the leather lighter. This is caused by the inborn property of soft leather to become darker after contact with moisture and grease.
Important! When clean leather is treated with moisture repellent product and the treated surface is exposed to liquid, then to avoid stains the liquid can easily be removed with a quick move or the leather can be wetted.