Urine in healthy people is odourless. The smell of ammonia is associated with the presence of diabetes and the smell of urea with impaired nitrogen balance - for example if you have consumed plenty of foods rich in proteins the previous day (beans, eggs, sheep yogurt, etc.) as foaming of urine is incidental effect which passes in a few days. Urine colour should be as lighter as possible and even transparent. Dark urine may indicate diseases of various kinds but mostly means you do not drink enough water.
A book about the 50 most common diseases, how to treat them and how to avoid generally being sick.