Gold IS yellow naturally.
There are a few ways to make gold be white, or any other shade: rose, green, black, etc. Other metals are added to the molten gold to make it 10, 14, 18 karat gold, and depending on what metals used, the colour can change as well. Often (mostly), “white” gold still has a yellow tinge to it, so a coating is added.
When you notice that your ring is “turning” yellow, it’s because the coating (almost always rhodium) is wearing off.
There are several reasons the plating may wear:
1. It wasn’t done properly in the first place.
2. Your own unique body chemistry which changes throughout the month.
3. Rubbing against other jewellery.
4. Exposure to chemicals, and yes, that includes hairspray.
5. Eventually, it will wear down, just like ANY metal, it gets thinner with use, and the rhodium plating is a VERY thin layer put on through a process called electroplating.
When I worked in the jewellery business (for nine years, I’m now a teacher), I discovered that the average time it takes for people to notice the wearing down of the rhodium is anywhere between 6 months and two years.
Now brides who NEVER need them replated, that’s usually because of the process which made the gold “white” in the first place. Some of these are not even dipped because they look like such a pure white.
I never had a customer ask me if their ring could be plated in platinum. Platinum is easily 3-4 times the cost of gold, so you’d be looking at a very expensive coating, and as it’s not the original manufacturers coating, your warranty (if you had one offered at time of purchase), would NOT cover the cost.
Even a platinum coating will eventually wear down, it may last 2-4 years. Platinum is known for its strength, but its not infallible.
I hope this helps!