Many multivitamin products also contain minerals such as calcium, iron, magnesium, potassium, and zinc. Minerals (especially taken in large doses) can cause side effects such as increased urination, But usually colour yellow is because of B- vitamin being taken but mostly the greenish yellow is common with a few people who takes multi vitamins so it is usually harmless but please recheck with your doctor if taking an extra mineral supplement to your multivitamin is necessary given the colour of the urine
Does not sound normal,either have it checked,or change to another to see if you have the same reaction,You do not say if it is combined with meds?