Unless you have a different colour scheme, the red line, or envelope is usually the LR pan envelope - the Volume envelope is usually blue. Highlight the track and press "V" to insert or remove the volume envelope.

Another way to reduce db on individual audio events is drag the top of the event downwards - you will see the waveform become smaller as you do this. This will reduce the whole event's db equally - to customise how you want to reduce or increase volume, the track envelope is better, as it can be ramped up or down by double clicking on the line to insert a node or pivot point then dragging.