Congratulations, you'd better buy a platinum ring. I have a gold and platinum, and the gold will change color and turn yellow after a long time. I also went to the shop assistant specially. The answer is that K gold contains other metals, which are not very pure and will turn yellow after a long time. If you want to buy it, you have to polish it, but if you polish it, it will wear out. But platinum won't. Mine has been several years.