Vitamin B 2 (riboflavin) is what gives your urine that vitamin yellow color. If it is being sent to a lab it can look yellow like antifreeze or clear like bottled water and as long as it passes specific gravity, creatinine clearance, and pH it will not matter. Some people who like to do the dilution method which calls for drinking a certain amount of fluids (sports drinks are preferred) like to put the color back in the urine. If you have done dilution before, you will have some idea what is enough and what is too much. Either way you can't fail just on color. They might be suspicious but the can't do anything as long as the 3 above mentioned parameters are within range. Some people who take instant dip stick tests such as for probation like to add the color back to their urine so that it has some yellow. If you raise suspicion during one of these tests all they can do is send it to a lab for confirmation. Sight alone cannot fail you.