Which colour change indicate(s) the ability of an organism to utilize citrate as a sole source of carbon in Simmon's citrate medium?

Which colour change indicate(s) the ability of an organism to utilize

1.	Which colour change indicate(s) the ability of an organism to utilize citrate as a sole source of carbon in Simmon's citrate medium?
Answer» f the medium turns BLUE, the ORGANISM is citrate POSITIVE. If there is no COLOR change, the organism is citrate negative.