Eye color is a polygenic phenotypic character determined by 2 distinct factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. Babies, who have European ancestry, their eyes color will change when the grow up. Because when they grow up, melanocytes begin to produce melanin, and melanocyte cells continually produce pigment to change eye color. Eye color will also change during puberty, pregnancy and after serious trauma as a result of chemical reactions and hormonal changes within the body. So normally, if you are an adult, it's not possible for you to get yellow eyes naturally, or you may get sick if you get yellow eyes suddenly. But you can wear yellow colored contact lenses to get yellow eyes.
I heard that there really rare people have such condition. Usually, hazel eyes are form of yellow and more orange and gold than anything. And till now, no one know hoe they inherited, but it exist. If you really like yellow eyes, you may have to wear yellow colored contact lenses which can make your eyes yellow.
Well, I must say it is impossible to get yellow eyes naturally. The color of eyes has been decided by two distinct factors: the pigmentation of the eye's iris and the light in the stroma of the iris. All these based on genes. We cannot change them unless wearing colored contact lenses and making up, even surgery. Personally, wearing yellow contact lenses is the fast and safest way to own yellow eyes. Many Hollywood famous stars always wear colored contact lenses to complete their performances. However, you must go to see a doctor and make sure that you are not allergic to contact lenses. Plus, pay attention to your hands in those germs in hands is easy to enter eyes when you touch them by hands. So wash them clean every time you touch contact lenses.