They won't test anything besides the urine in the cup. Toilet water is not tested. It is blue because it will discolor the specimen if the toilet water is added to the cup (so the urine can't be diluted from the toilet water). There was almost certainly a temperature strip on the cup, so they would have had you stay to collect another specimen if it was too cool (from adding water or bringing in urine from someone else). They are only testing for drugs, and running integrity tests to make sure it is human urine in the cup, and that nothing was added to it.