Forensic drugs testing. Image 2 of 3. Results of drugs tests to provide evidence against suspected drugs dealers. The blue colour indicates cocaine is present. The black colour indicates cannabis is present. The cocaine test involved using cobalt thiocyanate solution. The cannabis was tested with Duquenois Reagent (containing vanillin). Cocaine is an alkaloid drug obtained from the coca plant (Erythroxylon coca). Cannabis is obtained from the cannabis plant (Cannabis sativa). An amphetamine (shaboo, white crystals) is above the cannabis. For the result of a positive test on the amphetamine, see image H200/198. For the cocaine and cannabis before testing, see image H200/196.