Nail polish has long been considered inconsistent with wudu because the physical layer it creates over the nails prevents the penetration of water to the nails, which is a requirement for wudu. Therefore, a woman may pray while she has nail polish on but she has to take it off every time she needs to renew her wudu, which may mean taking it off and putting back on several times a day.
As much as women tried to beg for a way to put on nail polish and still pray, they couldn't find Islamic scholars to give them a break (that I know of.)
Yet, today I see more and more Muslim women who pray painting both their fingernails and toenails.
Who gave them a provision to do that? No one—many of them did it on their own.
This is my take on the matter: I could be wrong, but I pray that I will be rewarded for making an effort to help people enjoy life and enjoy their religion at the same time, and not see it as an arbitrary set of rules that make no sense.
Contemplating God as the Creator of the Universe creates a perception of God that is not as hard-headed as the "scholars" who make up rules on his behalf. I prefer to view God and His messenger differently.
I would imagine that the Prophet (PBUH) would be more flexible than these scholars. After all, if you contemplate "what would Muhammad do" based on what we know of him, we cannot imagine him preventing men and women from enjoying the beauties of life, just to apply a rigid rule that does not really have any practical benefits.
The Prophet was known to welcome objections and arguments. As far as I know, no one ever came to him asking for a provision and was denied it. If that was the case for the people who were around him at the time, why wouldn't it be the case for us today? Aren't we part of his Ummah too?
The Prophet's friends (yes they were called his friends, not his followers) didn't see him as a dictator, who dictates rigid rules. They saw him as a reasonable person with whom they could argue.
There are new things that come up everyday. Based on what we know about the Prophet, wouldn't he make accommodations for these new things? Or would he prefer that time stand still? New things came up during his lifetime and he accommodated them. Why would he expect time to stand still after his death?
Wudu, from the perspective of Maqased (purposes of Islamic law) is more of a ritual than anything else. It is meant for us to feel clean before prayer. Does making wudu without nail polish make you feel cleaner than when you have it on?
We wouldn't look at issues of science and medicine in such arbitrary rules without inspecting their practical purposes. Is religion at a lower level than science and medicine to be approached with different standards?
Nail polish is not a necessity, but why deprive ourselves from it?
So why is it important for some women to put on nail polish? This is a question that many clerics would ask. They would say that nail polish is not a necessity, so provisions are not in order.
The answer simply is that nail polish makes women's nails look prettier, and women have an instinctive desire to beautify themselves. Having beautiful things on you and around you makes you happier and for that matter closer to God. Neither God nor His Prophet would desire to deprive men or women of simple beauty—not based on my perception of them.
Henna and Kohl, although artificial beauty, were considered permission in traditional Islamic Law. The reason being that they were fashions that happened to be prevalent at the time of the Prophet. But times change and fashions change. Muftis cannot expect time to freeze. They also need to accept fashion as a social custom that will continually change. An old fashion isn't more conservative than a new fashion, because that old fashion used to be new at some point in time.
Nail polish today is perhaps equivalent to henna those days. While henna is a dye and nail polish is a physical layer, it is still a prevalent fashion today that the Prophet would likely have accommodated.
Is it worth the risk?
Some of them would say, since it is not a necessity, then there is no need to risk performing Islamic rituals in the wrong way, and perhaps not have any of your prayers counted in the eyes of God (yeah God would do that).
Perhaps their thinking is that God is somewhere in the sky and there's no way to know what his intentions are. We will never know what is acceptable and unacceptable by him until we meet him after we die. If it turns out that making wudu over nail polish was unacceptable, then we are in trouble. It is as if he is a person who is hiding and there is no way to communicate with him to know what he wants. There is no way to improve life and religion by experimentation and contemplation of life and the universe. Examining the Quran and the Hadith is the only way to know if we can make provisions regarding ibadat (Islamic rituals.)
God is near, God is here, and God is now. He is "Greater" than to be confined to a far away time or place.