When voting, a coloured ink is applied to the thumb nail.

Answer

If it is only ink, it does not form an impervious layer to prevent water. It should be washed thoroughly. The mark will not affect wudhu. Only if it forms an impervious layer as cutex does, will wudhu not be valid. We are not aware of the texture of the substance. If it is established that the substance remains on the nail as a non-porous layer, then it will not be permissible to vote because wudhu and ghusl will not be valid.