Q: grey audio tracks

Without more information it's difficult to say, but you may have accidentally muted the greyed tracks. Do any of your audio regions look greyed-out with a small blue circle in the top left like this?

Note that you can mute the entire track from the channel strip or by clicking on the track header mute button . . . however, the only way that all of your regions will turn grey is if you select the track and press "m" on your keyboard. You can also just mute/unmute individual regions on a track by selecting that region and pressing "m."