Food can also be a factor. The tint of all-natural edibles can interact with pigment to create a different color. Extremely processed foods can contain high amounts of food dye. This dye will work with pigment as well. If you do not apply water properly after exercise, it can also lead to dehydration and dark urine. Excessive exercise without proper hydration can cause serious side effects that lead to muscle wasting. Rare evidence suggests that bright yellow urine may be the first sign of pregnancy. These claims are not supported by studies.