The yellow color of urine is caused by the presence of urochrome. Urochrome is a pigment that is a byproduct of the breakdown of hemoglobin in the liver. During the breakdown of red blood cells, hemoglobin is broken down into a compound called bilirubin, which is then further metabolized into urochrome. Urochrome is excreted by the kidneys and gives urine its characteristic yellow color.

Option 1: Bile is a fluid produced by the liver and stored in the gallbladder. While bile does play a role in the digestion and absorption of fats, it is not directly responsible for the yellow color of urine.

Option 2: Lymph is a fluid that circulates throughout the body and plays a role in the immune system. Lymph is not involved in the coloration of urine.

Option 3: Cholesterol is a waxy substance found in the body and is involved in various functions, such as hormone production and cell membrane structure. Cholesterol does not contribute to the yellow color of urine.

In summary, the correct answer is option 4, urochrome, as it is the pigment responsible for the yellow color of urine.