I have a 1TB Time Machine which acts as a router and ONLY one of my four Mac’s back up on this machine. Recently it started blinking with a yellow light, so I though that there was a problem, and when I checked – it said that the drive was getting full. My settings on my TM backup are to delete the old backups to get more space as required. My question is what do I need to do, so that the light goes back to green?
— Nash
A Time Machine drive should get almost full, and then delete old files as it needs space. There's nothing for you to do. There's no reason for Time Machine to clear off space until it is needed -- you would rather have deeper backups than unused space on the hard drive. So just let TM do its job and don't worry about whether the light is green or yellow.