Which of the following is NOT a component of the SCBA that firefighters must check before use?

The correct answer is the color of the unit, as this is not a functional component that affects the operation or safety of the SCBA (Self-Contained Breathing Apparatus). Prior to using an SCBA, firefighters must ensure that critical components such as the air supply, harness fit, and regulator function are in proper working order.

Checking the air supply is essential because firefighters need to verify that there is enough breathable air for the intended duration of use. Harness fit is also crucial to ensure that the SCBA is securely worn and can be utilized safely during operations. The regulator's function must be tested to confirm that it is delivering the air effectively and reliably when needed.

While the color of the SCBA might be relevant for identification or aesthetic reasons, it does not impact its performance or safety, making it the correct choice as the component not required to be checked before use.