The ELISA (enzyme-linked immunosorbent assay) is a test which uses color change and antibodies to identify a substance. An indirect ELISA is one of three ELISA tests.
Urine varies in appearance, depending principally upon a body's level of hydration, as well as other factors. Normal urine is a transparent solution ranging from colorless to amber but is usually a pale yellow. In the urine of a healthy individual the color comes primarily from the presence of urobilin.
Dark yellow yes: Dark yellow urine is normal in the morning because it is concentrated because you are not drinking water while sleeping. If however, it is brownish like tea, that may mean there is blood in it. If you think it is a bit brown you should see a doctor for an urinalysis. ...Read more.