The present invention provides a method involving at least one first circuit having at least one first input, at least one second input, and at least one output. The transmitter is positioned external to the housing, and the receiver is positioned to receive the beam of radiation. The devices are typically removable devices that may be placed over or in a respiratory cavity to increase resistance to airflow within the respiratory cavity. The color identification information determining portion determines first color identification information of a color type corresponding to the first color information, and second color identification information of a color type corresponding to the second color information, by referring to color correlations.