If a test kit displays a blue with pink color, which drug is most likely being tested?

• A. Cocaine
• B. Meth
• C. Marijuana
• D. Heroin

Answer: (A)

Colorimetric presumptive tests rely on specific reagent reactions that produce distinctive colors for different drugs. In the cocaine-detecting kit (the Scott-type test), cocaine presence causes the organic layer to take on a blue color, and the pattern can appear as blue with a pink element after the subsequent steps. That blue appearance is a characteristic signature of cocaine in this particular test. Other drugs yield different color changes with the same kit (meth tends toward orange/brown with common reagents, marijuana usually shows purple with Duquenois–Levine, heroin can produce purple or brown with related tests). So, witnessing a blue color accompanied by pink is most consistent with cocaine being tested.