Final answer:
The color change in a field drug test kit for methamphetamine after breaking the last ampoule may vary and is not provided, making it difficult to provide an accurate response.
Step-by-step explanation:
When methamphetamine tests positive in a field drug test kit, the color that it turns after breaking the last ampoule typically varies based on the specific type of test kit used. However, the question does not provide sufficient information about the type of field test kit being referred to, but a commonly used field test kit for methamphetamine is the Marquis reagent, which would turn orange-brown when it comes in contact with methamphetamine. If we are discussing a different type of test where blue-green is mentioned as a positive result, and other examples such as a breathalyzer reaction turning green indicating ethanol presence or a VRLD test resulting in a bright pink color for positive syphilis, then it's possible that options A) Blue, B) Purple, or D) Yellow are incorrect, and so the answer may be C) Pink, but this is speculative due to insufficient information provided.