My urine is a neon yellow color and I don't take vitamins. What could cause this and should I be worried? I drink water and eat ice all day long

Urine color. Normal urine color ranges from very pale yellow/or clear (when it is very dilute) to dark yellow, almost brown when it is extremely concentrated (i.e. You're not drinking enough fluids). The color is affected by certain dyes in foods, a common one is due to the riboflavin vitamin you mentioned. As long as it continues to vary in this range, being mostly yellow, there is nothing to worry about.
Unclear but. Urine color is a function what people eat and other factors like concentration or infection. You did not mention medication. It is possible that a medicine is causing it. You can try to change your diet completely for 1-2 days and see what happens. Drinking too much water is not useful for people except in cases of kidney stones. It can cause edema and heart failure if the person is not healthy.