What color does the M9 detector indicate with chemical agents?

The M9 detector is specifically designed to detect the presence of chemical agents on surfaces. When the M9 tape comes in contact with chemical agents, it changes color, with purple being one of the primary indicators for nerve agents, red-brown for blister agents notably like mustard gas, and pink for certain other chemical agents. The presence of various colors on the M9 tape allows for quick identification of different types of chemical threats. Therefore, it is accurate to state that the M9 detector can display multiple colors indicating various chemical agents, making "all of the above" the correct answer, as it encompasses all the color changes that may occur in response to different substances.