If you are referring to nail polish on the fingers of the hand, it has to be completely removed before wudhu. If you are referring to nail polish on the feet toes, then as per Sayed Taqi Modaressi, wiping of the feet must be done using three fingers based on precaution. Precaution here means you are able to refer to the next most A'lam scholar (most knowledgeable). For example Ayatullah Sistani allows wiping of the feet to be of any width