Insulin is a naturally occurring hormone made by the pancreas that helps our body use or store the glucose (sugar) it gets from food. For people with diabetes, either the pancreas does not make enough insulin to meet the body's requirements, or the body cannot properly use the insulin that is made.
The yellow color in normal urine comes from a substance known as urochrome. Urochrome is also known as urobilin and is the result of hemoglobin breakdown. Hemoglobin is the protein in red blood cells that enables oxygen to be taken around the body.
Well, that's difficult to say. It probably means nothing. Yellow is the color we expect urine to be. If you take a vitamin supplement, these can sometimes give the urine an almost fluorescent color, a very bright yellow or yellow-green. That's just due to the dyes in the vitamin. If you've eaten anything recently with yellow dye in it, that could also be a reason for bright yellow urine.