<prompt> Ferric chloride test in PKU givesGreenRedYellowBlue  <response>: Urine of the patient contains phenylketones about 500- 3000 mgday . This could be detected by adding a drop of ferric chloride to the urine . A transient blue - green color is a positive test. But this is a less reliable test. Ref : DM.VASUDEVAN.TEXTBOOK ; SEVENTH EDITION ; PAGE NO : 237. 