All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If this kohl prevents water from reaching the skin, then ablution is not valid and Ghusl (ritual bath) is not valid; so, one has to remove it to allow water reaching the skin. It is a condition for the validity of ablution and Ghusl that water should reach the skin of the washed limb. However, if this kohl does not have any size [volume, thickness], but it just leaves its effect on the skin like the stone kohl, then there is no harm in using it, and ablution is valid as this kind of kohl does not prevent water from reaching the skin.
Allaah Knows best.